(SECOND    EDITION) 


STANDARD  LIGHTING 

WITH    INCANDESCENT   ELECTRIC   LAMPS 

COMPILED  BY 

A   STAFF   OF   EXPERTS 

Endorsed  by  the  Lighting  Department  of  the  Joint  Com- 
mittee for  Business  Development  in  the  movement  to 
" Electrify"  and  by  the  Society  for  Electrical  Development. 

The  movement  for  Business  Development  is  being  promoted  by 
the  following  national  organisations:  National  Electric  Light 
Association;  Electrica[  Supply  Jobbers'  Association;  National 
Association  of  Electrical  Contractors  and  Dealers;  National 
Council  of  Lighting  Fixture  Manufacturers;  Lighting  Fixture 
Dealers'  Society  of  America;  Illuminating  Glassware  Guild; 
Illuminating  Engineering  Society;  Electrical  Manufacturers' 
Council;  The  American  Institute  of  Electrical  Engineers. 


In  the  preparation  of  this  text,  the  aim  has 
been  to  present  information  of  real,  practical 
value  both  to  the  purchaser  and  to  the  in- 
staller of  lighting  equipment. 

Analysis  of  available  information  revealed 
that  in  the  transactions  of  the  Illuminating 
Engineering  Society  and  in  the  publications 
of  the  manufacturers  of  lighting  equipment 
was  to  be  found  the  most  exhaustive,  clearest, 
and  most  up-to-date  discussion  of  many  of  the 
more  important  lighting  problems. 

These  publications  have,  therefore,  been 
freely  used  in  the  compilation  of  this  handbook. 
Acknowledgement  is  gratefully  made  to  S.  E. 
Doane,  G.  H.  Stickney,  D.  W.  Atwater,  A.  B. 
Oday,  Ward  Harrison,  A.  L.  Ppwiell,  S.  G. 
Hibben,  H.  A.  Smith,  R.  E.  Harrington,  A.  S. 
Turner,  C.  A.  Atherton,  M.  Luckiesh,  Earl  A. 
Anderson,  J.  H.  Kurlander,  G.  A.  Clewell,  H.  H. 
Magdsick  and  J.  R.  Colville  for  permission  to  use 
material  prepared  by  them  and  for  constructive  sug- 
gestions in  the  presentation  of  the  subjects. 


INDEX    TO    CONTENTS    PAGE    269. 

PUBLISHED  BY 
H.  C.  CUSHING,  JR.,  8  WEST  4OTH  ST.,  NEW  YORK,  U.S. A, 


Copyright,    1922 

by 
H.  C.  GUSHING,  JR. 


TABLE  OF  CONTENTS 

Page 

ILLUMINATION    FUNDAMENTALS— PART    1 5 

Amount  of  Light — Diffusion  of  Light — Color  Quality  of  Illumi- 
nation —  Shadow  —  Uniformity  of  Illumination  —  Illumination  of 
Vertical  Surfaces — Desirable  Wall  Brightness — Maintenance. 

ILLUMINATION  DESIGN  DATA— PART  II 14 

Definitions — Foot-Candle  Illumination — Type  of  Lighting  Unit — 
Location  of  Outlets,  Mounting  Height,  and  Number  of  Lighting 
Units — Lamp  Size — Computed  Illumination  Values — Illustrative  Prob- 
lem— Guide  to  the  Selection  of  Reflecting  Equipment,  Chart — Spacing 
— Mounting  Height,  Table — Foot-Candles  Illumination,  Tables — 
Coefficient  of  Utilization,  Table — Room  Index,  Tables — Lumen  Output 
of  Mazda  Lamps,  Table — Computed  Illumination  Values,  Table. 

STORE  AND  SHOW  WINDOW  LIGHTING— PART  III 46 

General  Classes  of  Store  Lighting — Amount  of  Illumination  Required 
— Lighting  Units  or  Luminaires— Lamps  Recommended  for  Use,  Table 
— Entrance  Doorway  Lights — Night  Lights — Wiring  and  Control — 
Color  Matching  and  Color  Quality— Showcase  Lighting— Illustrative 
Problems — Show  Window  Lighting — Show  Window  Equipment — 
Show  Window  Illumination  Calculations. 

INDUSTRIAL    LIGHTING— PART    IV 63 

Requirements — Light  on  the  Work — Daylight  Intensities,  Table — 
Illumination  of  Surrounding  Surfaces — Color  Quality  of  Light — Glare 
—Specular  Reflection— Shadows— Locations  of  Outlets— Work 
Bench  Lighting — Chart  for  Effecting  Lighting  Improvements — 
115  vs.  230  Volt  Lamps. 


LIGHTING     OF     OFFICE     BUILDINGS     AND      DRAFTING 

ROOMS— PART  V 89 

Introduction — Method  of  Lighting — Comparison  of  Lighting  Systems 
— Spacing  of  Outlets — Wattage  Required — Drafting  Rooms. 

SCHOOL  LIGHTING— PART  VI 98 

Introduction  —  Illumination  Values — Diffusion — Classrooms— General 
Considerations — Blackboards — Comparison  of  Various  Lighting  Sys- 
tems—Corridor—Laboratory— Auxiliary  Outlets. 


RESIDENCE  LIGHTING— PART  VII 105 

Introduction  —  Systems  of  Lighting  —  Kitchen  —  Butler's  Pantry  — 
Laundry  and  Work  Bench — Den  or  Sewing  Room — Living  Room — 
Dining  Room — Hall  or  Reception  Room — Bed  Room — Bath  Room — 
Porch — Grounds — Garage — Wiring — Recommended  Sizes  of  Lamps, 
Chart. 

CHURCH  LIGHTING— PART  VIII 125 

General  Requirements — Methods  to  Avoid — Feasible  Schemes  for 
Lighting  —  Ritualistic  Churches  —  Evangelical  Churches  —  Special 
Lighting  Requirements — Chancel — Choir  Loft — Windows — Wiring. 

LIGHTING  OF  PUBLIC  BUILDINGS— PART  IX 135 

Armories — Gymnasiums — Main  Exercising  Floor — Swimming  Pool — 
Running  Track — Exercising  Rooms — Shower  and  Locker  Rooms — 
Art  Galleries — Paintings — Statuary — Museums — Libraries — Municipal, 
County,  and  State  Buildings — Banks. 

LIGHTING     OF     HOSPITALS     AND     DENTAL     OFFICES- 
PART  X 1 54 

Wards — Private  Rooms — Corridors — Operating  Rooms — Wiring  and 
Signal  Systems — Dental  Offices. 

FLOODLIGHTING— PART  XI 166 

Equipments — Typical  Installations. 

LIGHTING  FOR  OUTDOOR  SPORTS— PART  XII 182 

Tennis  Courts — Clock  and  Court  Golf — Motorcycle  and  Bicycle 
Racing — Outdoor  Arenas — Bathing  Beaches — Trap  Shooting  Ranges. 

LIGHTING  FOR  INDOOR  RECREATIONS— PART  XIII 191 

Pool  and  Billiard  Parlors — Bowling  Alleys — Indoor  Tennis  Courts — 
Squash  Courts — Skating  Rinks. 

MAINTENANCE     OF     INTERIOR     LIGHTING     SYSTEMS- 
PART  XIV 199 

Extent  of  Lighting  Depreciation — Value  of  Light  Wasted — Systematic 
Maintenance— Suggestions  for  Restoring  a  Lighting  System,  Chart. 

MODERN  PRACTICE  IN  STREET  LIGHTING— PART  XV 207 

Principal  Business  Streets  —  Thoroughfares  —  Residence  Streets  — 
Outlying  Districts  and  Alleys  —  Highways  —  Summary  of  Modern 
Practice,  Table — Necessity  of  Maintenance. 

ELECTRICAL  ADVERTISING— PART  XVI 2ig 

Forms  of  Electrical  Advertising— Exposed  Lamp  Signs— Enclosed 
Lamp  Signs— Bulletin  and  Poster  Boards— Building  Outline  and  Mar- 
quee Lighting— Flood-lighted  Advertising— Sign  Maintenance. 

CODE  OF  LIGHTING— PART  XVII 233 

The  Code  of  Lighting  for  Factories,  Mills  and  Other  Work  Places 
prepared  and  issued  by  the  Illuminating  Engineering  Society. 


PART  I 
ILLUMINATION  FUNDAMENTALS 

In  the  last  year  of  the  war  and  in  the  year  immediately  fol- 
lowing, more  progress  was  made  in  the  application  of  artificial 
lighting  than  in  any  ten-year  period  preceding.  Continual  im- 
provements in  lamps  and  reflecting  equipments,  the  constantly 
increasing  availability  of  electric  service,  and  the  growing  knowl- 
edge of  illumination  fundamentals,  had,  over  a  period  of  years, 
been  paving  the  way  for  a  sudden,  sharp  advance  in  lighting 
practice. 

In  no  field  of  lighting  was  the  progress  so  remarkable  as 
in  industry,  for  here  the  value  of  good  illumination  could  be 
most  easily  measured  in  terms  of  dollars  and  cents.  Tests  con- 
ducted under  actual  working  conditions  demonstrated  that 
startling  increases  in  production  were  possible  when  antiquated 
lighting  systems  were  replaced  with  new  ones  which  produced 
lighting  comparable  with  the  daylight  lighting  of  well  designed 
modern  factories.  Most  executives  believed  in  good  lighting,  they 
acknowledged  its  importance,  but  what  they  did  not  know,  and 
what  had  not  been  satisfactorily  demonstrated,  was  that  what 
were  then  considered  good  lighting  installations  we're  not  sup- 
plying enough  light ;  in  other  words,  were  not  good  lighting. 
Once  the  traditional  illumination  levels  were  broken  through 
and  levels  3,  4,  and  5  times  as  high  tried  out  in  service,  the  handi- 
cap imposed  by  previous  standards  became  apparent.  Artificial 
lighting  in  every  field  moved  forward. 

Amount  of  Light 

We  do  not  know  today  how  much  light  is  right  for  the  many 
applications.  We  do  know  that  3  or  4  foot-candles  will  enable 
one  to  see  more  detail  than  will  1  foot-candle;  that  10  foot- 
candles  will  reveal  more  than  3  or  4;  that  50  foot-candles  will 
increase  perception  over  10;  that  100,  or  even  more,  will  some- 
times produce  still  further  improvements  when  the  eyes  are  taxed 
to  the  utmost.  We  know  that  vision  is  quickened  when  the 
illumination  is  increased  from  2  or  3  foot-candles  to  10,  50,  or  to 
100  or  more.  We  know  that  persons  with  defective  vision,  and 
this  means  a  surprisingly  large  proportion  of  the  people,  are  even 
more  greatly  handicapped  by  poor  lighting  than  are  those  with 
good  vision,  and  that  they  respond  more  markedly  to  improve- 
ment in  the  lighting.  Again  we  know  that  bright  and  cheerful 
surroundings  are  stimulating,  that  they  inspire  cleanliness,  that 


they  make  for  order  and  neatness.  In  these  simple  fundamental 
facts  we  find  the  reasons  why,  in  industry,  higher  levels  of  illu- 
mination increase  production  without  imposing  strain  upon  the 
employees,  why  they  automatically  reduce  accident  hazard,  de- 
crease spoilage,  and  improve  morale ;  why,  in  the  office,  they 
enable  more  work  to  be  performed  with  fewer  headaches,  less 
mistakes,  and  better  tempers;  why,  in  the  store,  they  attract 
customers,  facilitate  the  examination  of  material,  and  make  for 
quicker  sales ;  and  why,  in  the  home,  they  facilitate  reading, 
working  or  studying  at  night. 
Diffusion  of  Light 

With  the  10  to  1  increase  in  efficiency  of  the  incandescent 
lamp,  since  its  invention  scarcely  two-score  years  ago,  has 
come  the  generation  of  large  volumes  of  light  in  a  small  space. 
This  means,  of  course,  light  sources  of  great  brilliancy.  A 
bright  source  does  not  in  itself  insure  adequate  lighting,  in  fact, 
unless  skillfully  handled,  it  presents  a  positive  menace  to  vision. 
Objects  are  seen  by  the  light  which  comes  from  them  to  the 
eye;  light  which  comes  directly  from  the  light  source  to  the 
eye  or  is  reflected  from  the  source  to  the  eye  by  some  polished 
surface  is  not  only  useless  in  illuminating  the  object  viewed  but 
if  of  high  intensity  or  of  large  volume,  it  produces  a  blinding  ef- 
fect which  seriously  interferes  with  seeing  and  may  result  in 
permanent  injury  to  the  eyes.  "Glare"  is  the  term  applied  to  light 
which  obstructs  vision  in  this  way. 

Glare  blinds  the  driver  of  an  automobile  when  approaching 
another  with  improperly  adjusted  headlights  at  night;  it  handi- 
caps the  workman  who  is  trying  to  see  fine  details  with  a  bril- 
liai::  light  source  near  his  line  of  vision;  it  produces  acute  dis- 
comfort in  the  conference  room  where  men  sit  facing  inade- 
quately shaded  windows  for  a  long  period  of  time;  it  is  annoying 
in  the  home  where  wall  brackets  containing  unshielded  lamps 
are  seen  against  dark  backgrounds ;  it  blinds  the  ball  player,  who 
tries  to  follow  the  ball  against  the  sun.  In  hundreds  of  ways 
it  is  constantly  interfering  with  vision  and  handicapping  us  in 
work  and  play. 

Specular  reflection,  that  is,  the  reflections  of  light  sources 
in  polished  surfaces,  while  sometimes  an  aid  to  vision,  is  often, 
because  of  its  insidious  nature,  more  harmful  than  direct  glare. 
Under  proper  control,  it  facilitates  the  reading  of  the  micrometer 
scale  or  the  inspection  of  a  polished  surface ;  in  excess,  it  be- 
comes reflected  glare,  dulls  perception,  and  paves  the  way  for 


accident.  As  moderate  specular  reflection,  it  brings  out  the 
texture  of  materials  and  assists  the  housewife  in  her  sewing;  as 
reflected  glare,  it  blurs  the  printed  page  and  causes  eyestrain 
in  reading.  In  small  amounts,  coming  from  the  pavement  to  the 
eye  it  discloses  the  inequalities  of  the  road  to  the  motorist  at 
night  or  reveals  the  pedestrian  in  silhouette;  in  large  amounts, 
as  from  snow  in  sunlight,  it  produces  painful  and  serious  injury 
to  the  eyes. 

Fortunately,  once  the  danger  in  direct  glare  and  the  advan- 


Had  only  one  row  of  units  been  employed  in  lighting  this  store,  as  is  quite 
commonly  the  case  with  small  stores,  the  center  aisle  would  have  been 
brightly  lighted,  but  much  less   light  would  fall  on  the  counters 
where  most  needed  and  a  customer  would  inevitably  cast  a 
shadow  on  the  merchandise.     Note  the  soft  even  illumina- 
tion shown  in  this  illustration  where  correct  principles 
have  been  followed 

tages  and  disadvantages  in  specular  reflection  are  understood, 
the  means  for  eliminating  the  bad  and  retaining  the  good  is 
readily  available.  The  answer  lies  in  proper  diffusion  of  the 
light.  The  reflecting  equipments  now  regularly  manufactured 
provide  any  degree  of  diffusion  considered  desirable.  The  to- 
tally indirect  type  which  directs  all  of  the  light  to  the  ceiling, 
whence  it  is  diffused  throughout  the  room,  represents  the  ut- 


most  in  diffusion;  the  semi-indirect  type,  which  directs  a  large 
proportion  of  the  light  to  the  ceiling,  but  transmits  some 
through  the  bowl,  provides  a  degree  of  diffusion  which  is  pre- 
ferred by  many;  so-called  light-directing  semi-enclosing,  or  to- 
tally enclosing,  units  are  available  in  designs  which  provide  good 
control  of  the  light  and  satisfactory  diffusion;  enclosing  globes 
of  the  proper  size  and  density  provide  diffusion  of  the  light  but 
afford  little  control  of  its  distribution.  Open  reflectors  of  proper 
design  eliminate  glare  from  the  lamp  filament  but  afford  no 
protection  against  reflected  glare  in  polished  surfaces.  Such  re- 
flectors, however,  when  designed  for,  and  used  with,  bowl- 
enameled  lamps  constitute  an  equipment  which  is  almost  ideal 
for  the  large  majority  of  industrial  applications.  They  are  in- 
expensive, easy  to  maintain,  allow  considerable  control  of  the 
light  distribution,  provide  good  diffusion,  and  eliminate  objec- 
tionable specular  reflection  while  at  the  same  time  producing 
sufficient  glint  for  the  reading  of  a  scale  or  the  examination  of 
textiles. 

Color  Quality  of  Illumination 

Since  an  object  is  seen  by  the  light  which  comes  to  it  from 
the  source  and  thence  by  reflection  to  the  eye,  it  follows  that 
color  in  the  object  is  seen  only  when  the  light  contains  rays  of 
that  color.  For  example,  a  red  object  will  appear  black  under 
light  in  which  red  rays  are  lacking  or  a  blue  object  will  appear 
black  when  blue  rays  are  absent  in  the  source.  Daylight  is 
composed  of  all  the  colors  in  proportions  seen  in  the  rainbow 
The  light  from  Mazda  lamps  contains  all  the  colors  composing 
daylight  but  if  the  spectra,  or  rainbows,  of  the  two  were  to  be 
compared  it  would  be  seen  that  the  Mazda  lamp  was  richer 
than  daylight  in  the  orange-red  region  and  weaker  in  the  blue. 
For  ordinary  purposes,  the  light  from  clear  Mazda  lamps  is 
sufficiently  like  daylight  to  answer  all  requirements,  but  where 
color  discrimination  is  a  factor,  as  in  sorting  or  grading  pro- 
cesses for  example,  and  in  the  laundry  where  scorch  marks  must 
be  readily  distinguishable,  or  where  the  artificial  light  is  used 
to  supplement  daylight,  as  in  an  office,  daylight  lamps,  which 
screen  out  the  majority  of  the  excess  orange-red  rays,  find  wide 
application. 

For  purposes  of  color  matching,  dyeing,  process  printing,  and 
the  like,  where  extreme  accuracy  is  necessary  in  the  observation 
of  colors,  a  still  further  correction  of  the  light  is  necessary. 
For  this  service  so-called  color-matching  units,  which  provide 


a  light  of  true  and  unvarying  north-sky  quality,  are  available. 

The  high  efficiency  of  present  incandescent  lamps  which 
makes  practicable  the  approximation,  or  the  duplication,  of  day- 
light on  a  large  scale  also  permits  the  modification  of  light  to 
any  desired  extent  for  obtaining  striking  and  unusual  effects 
in  display  windows,  in  decorative  lighting,  and  in  the  home. 

Equipments  designed  especially  for  the  control  of  color  are 
readily  available. 
Shadow 

Contrary,  perhaps,  to  popular  opinion,  a  certain  amount  of 


Correct  lighting  for  every  service  conforms  to  certain  fundamental  prin- 
ciples.  Note  the  evenness  of  illumination,  the  absence  of  sharp  shadows, 
and  the  bright  and  cheerful  appearance  of  the  interior 

shadow  is  desirable  in  artificial  lighting.  Objects  illuminated 
by  perfectly  diffused  light  appear  flat  and  uninteresting,  con- 
tours are  lost,  and  it  is  difficult  for  the  eye  to  form  a  correct 
judgment  of  the  shape  of  an  object.  On  the  other  hand,  deep, 
black  shadows  are  troublesome  and  are  a  source  of  constant 
danger  because  of  what  they  may  conceal.  Shadows  having  a 
sharp  edge  or  a  series  of  sharp  edges,  which  result  from  several 
small  light  sources  near  one  another,  are  particularly  annoying 
in  office  work,  where  they  dance  about  the  pencil  point  most 
disconcertingly.  In  general,  in  interior  lighting,  only  soft 


illuminated  shadows  with  gradually  fading  outlines  should  b^ 
tolerated. 

The  number  of  shadows  cast  by  an  object  and  their  length 
depends  upon  the  number  and  the  position  of  sources  directing 
light  toward  the  object;  the  softness  of  the  shadow  depends  upon 
the  area  of  the  surfaces  from  which  the  light  comes  and  upon 
the  number  of  directions  from  which  light  is  received.  Indirect 
and  dense  semi-indirect  units  which  make  the  ceiling  serve  as 
the  principal  light  source,  and  large  units  of  the  direct-lighting 
type,  therefore,  make  for  soft  shadows,  small  units  of  the  direct 
type  make  for  sharp  shadows.  As  a  general  rule,  lighting  units 
which  are  satisfactory  for  the  application  from  the  standpoints 
of  light  diffusion  and  low  brightness  will  also  prove  satisfactory 
from  the  standpoint  of  shadow  when  a  sufficient  number  are 
used  to  provide  a  satisfactory  degree  of  uniformity  in  the  light- 
ing of  the  work. 

Uniformity  of  Illumination 

Where  the  prime  purpose  of  lighting  is  the  production  of 
artistic  effects,  uniformity  of  illumination  may  be  undesirable. 
On  the  other  hand,  it  is  not  an  uncommon  experience  to  find 
in  industrial  plants  that,  because  of  too  great  a  spacing  between 
units,  some  workmen  are  supplied  with  only  one  half  or  one  third 
as  much  light  for  their  work  as  are  others.  Many  office  employees 
are  forced  to  work  under  the  same  handicap.  There  are  cases  on 
record  where  the  suspected  incompetency  of  an  employee  with 
respect  to  his  co-workers  has  been  traced  to  the  unsuspected 
cause  of  poor  lighting. 

Definite  relations  exist  between  the  height  at  which  units 
are  mounted  above  the  work  and  the  distance  by  which  they 
may  be  separated  to  provide  reasonable  uniformity  in  lighting, 
and  light  from  a  sufficient  number  of  directions  so  that  shadows 
will  not  prove  troublesome.  These  relations  have  been  reduced 
to  simple  tabular  form  for  the  convenience  of  the  designer  of 
lighting  systems.  In  general,  the  permissible  distance  between 
units  should  not  be  more  than  one  and  one-half  times  the  height 
of  the  light  sources  above  the  work ;  closer  spacings  can  do  no 
harm  and  are  often  desirable  but  when  this  spacing  distance  is 
exceeded,  the  illumination  between  units  falls  off  very  rapidly. 
The  user  of  light  should  consider  carefully  before  allowing  his 
desire  to  keep  initial  costs  low,  lead  him  to  install  a  system  in 
which  the  proper  spacing  distance  is  materially  exceeded. 

10 


Illumination  of  Vertical  Surfaces 

For  many  locations,  such  as  offices  and  drafting  rooms,  light 
is  required  principally  on  horizontal  planes,  such  as  desk  tops  or 
table  tops,  and  it  has  been  the  custom  to  calculate  illumination 
on  the  basis  of  that  delivered  to  horizontal  surfaces  with  the 
assumption  that  the  oblique  surfaces  of  objects  would  be  suffi- 
ciently lighted.  This  practice  may  result  in  inadequate  illumina- 
tion. In  a  machine  shop,  for  example,  the  lighting  of  the  vertical 
surfaces  of  the  work  or  of  machine  parts  is  fully  as  important  as 


There  is  no  necessity  for  imposing  a  handicap  on  any  worker  because  of 

poor    light.      Though    illumination    requirements    for    drafting    rooms 

are  comparatively   severe  on   account  of   close  visual   application, 

these  requirements  are  met  by  the  uniform,  thoroughly  diffused, 

shadowless   illumination   of    high    intensity   shown   here 

the  lighting  of  the  horizontal  surfaces.  As  a  matter  of  fact, 
most  shops  are  lighted  during  the  day  by  light  from  windows, 
which  give  a  greater  light  on  the  vertical  surfaces  than  on  the 
horizontal.  In  all  such  cases  where  direct  lighting  is  used,  only 
those  lighting  units  should  be  installed  which  show  a  reasonably 
good  candlepower  in  the  50-70  degree  zone  as  well  as  below  these 
angles.  A  shop  lighted  by  closely  spaced  automobile  head- 
lights directing  the  light  downward  from  the  ceiling  would 


furnish  ample  light  on  a  horizontal  plane  but  such  lighting  would 
be  far  from  satisfactory. 

Desirable  Wall  Brightness 

The  effectiveness  of  a  lighting  system  depends  not  only  on 
the  effectiveness  of  the  lighting  unit,  but  also  on  the  reflecting 
properties  of  the  walls,  ceiling,  and  surroundings,  and  upon  the 
size  and  proportions  of  the  room.  It  is,  in  fact,  entirely  pos- 
sible to  find  an  installation  of  reflectors  of  poor  design  and  in- 
ferior from  the  standpoint  of  glare,  which  is  nevertheless,  from 
the  single  standpoint  of  the  percentage  of  light  reaching  the 
illumination  plane,  better  than  an  installation  where  reflectors 
of  good  design  are  used,  if  the  former  are  installed  under  favor- 
able conditions  such  as  light  walls,  ceiling,  etc.,  and  the  latter 
under  unfavorable  conditions.  On  the  other  hand,  it  must  be 
borne  in  mind  that  a  large  expanse  of  wall  surface  finished  so 
light  as  to  reflect  a  large  volume  of  light  into  the  eyes  is  objec- 
tionable for  offices,  residences,  and  all  rooms  where  the  occu- 
pants are  likely  to  sit  more  or  less  directly  facing  the  walls  for 
considerable  periods  of  time.  Such  data  as  are  available  indicate 
that  where  the  brightness  of  the  walls  is  equal  to,  or  greater  than, 
the  brightness  of  white  paper  lying  on  a  table  or  desk,  annoying 
glare  will  result.  In  fact,  a  wall  brightness  one-half  that  of  the 
paper  has  been  found  unsatisfactory — a  brightness  of  one-fifth 
is,  apparently,  comfortable.  With  the  usual  types  of  lighting 
units,  walls  are  not  illuminated  to  intensities  as  high  as  those 
obtaining  on  desk  or  table  tops,  and  walls  which  reflect  less  than 
50  per  cent,  of  the  light  which  strikes  them  should  not  produce 
discomfort,  providing,  of  course,  that  they  are  of  a  mat  or  semi- 
mat  finish.  Walls  finished  in  buff,  light  green,  or  gray  reflect 
about  the  proper  proportion  of  light  and  their  use  is  meeting  with 
general  favor.  Walls  finished  in  a  high  gloss  are  not  satisfac- 
tory from  a  glare  standpoint. 

Maintenance 

The  experiences  of  those  who  have  installed  high  levels  of 
illumination  prove  conclusively  that  every  foot-candle  delivered 
at  the  work  has  a  definite  tangible  value. 

The  man  who  provides  a  system  capable  of  delivering  10 
foot-candles  at  the  work  and  then  allows  the  system  to  de- 
preciate until  it  delivers  only  3  or  4  is  losing  not  only  60  or  70 
per  cent,  of  the  light  he  is  paying  for  but,  what  is  far  more  im- 
portant, he  is  losing  the  profit  on  the  difference  between  the 


12 


output  of  his  employees  at  this  low  level  of  illumination  and 
their  output  at  the  higher  level.  If  the  depreciation  of  a  lighting 
system  were  of  the  order  of  2  or  3  per  cent,  or  even  10  per  cent, 
the  matter  would  not  be  so  serious  a  one,  but  surveys  of  in- 
stallations in  service  show  depreciations  of  50  per  cent.,  60  per 
cent.,  and  more.  Many  users  are  not  getting  one  third  of  the 
light  their  systems  are  capable  of  delivering. 


The   lighting   of   the   home   should  be   flexible   to   permit    lighting   effects 
suitable  to  various  occasions  to  be  obtained,  but  in  all  cases,  the  funda- 
mentals of  lighting  hold.     All  bright  lights  should  be  adequately 
shielded  from  view,  though  enough  light  should  be  available 
for  reading  or  sewing  comfortably. 


13 


PART  II 
ILLUMINATION   DESIGN   DATA 

To  take  the  several  essential  factors  entering  into  illumina- 
tion design  properly  into  account  has  appeared  so  complicated 
a  task  that  many  designers  have  adhered  to  rule-of-thumb  meth- 
ods which,  while  adequate  in  some  cases,  are  likely  to  lead  to 
unsatisfactory. results  when  applied  generally. 

The  method  of  design  here  presented  will  be  found  fully  as 
simple  as  any  of  the  common  short-cuts.  It  has  the  decided  ad- 
vantage that  the  technical  considerations  wjhich  are  important  as 
influencing  the  result  and  which  require  the  experienced  judg- 
ment of  the  engineer  have  been  taken  into  account  in  the  prep- 
aration of  the  charts  and  tables  and  therefore  automatically  re- 
ceive due  allowance  in  the  lighting  design.  The  data  apply  in 
interiors  where  standard  types  of  reflecting  equipment  are  used 
to  obtain  general  lighting  of  substantially  uniform  intensity. 

The  four  steps  to  be  carried  out  in  the  design  of  a  general 
lighting  system  for  a  room  are : 

1.  Decide  the  foot-candle  illumination  required. 

2.  Select  the  type  of  lighting  unit  best  adapted  to  the  loca- 
tion. 

3.  Determine  the  location  of  outlets,  the  mounting  height 
and  number  of  lighting  units  required. 

4.  Ascertain  the  size  of  MAZDA  lamp  which  will  provide  the 
foot-candles  desired. 

i.  Foot-Candle  Illumination 

Tables  3  and  4,  pages  25  to  31,  list  the  foot-candle  values,  cor- 
responding to  present  standards,  for  different  classes  of  indus- 
trial operations,  offices,  stores,  etc.  The  desirable  illumination 

DEFINITIONS 

Lumen:  The  lumen  is  the  unit  of  light  flux  quantity.  The  number  of  lumens  re- 
quired to  light  a  given  surface  is  proportional  to  the  illumination  in  foot-candles  and  to 
the  area  of  the  surface  in  square  feet.  The  light  output  of  MAZDA  lamps  is  given  in  lumens. 

Foot-Candle :  The  degree  to  which  a  surface  is  illuminated  is  measured  in  foot-candles. 
One  lumen  will  light  a  surface  of  1  square  foot  to  an  average  intensity  of  1  foot-candle. 

Coefficient  of  Utilization  (Percentage  Of  Lumens  Effective) :  The  proportion  of  the 
lumens  generated  by  the  lamps  which  reaches  the  plane  of  work  is  known  as  the  Co- 
efficient of  Utilization.  It  is  dependent  upon  the  type  of  diffusing  and  reflecting  equip- 
ment, color  of  walls  and  ceiling  and  also  the  proportions  of  the  room,  that  is,  the  size 
and  shape  of  the  room  and  the  height  of  the  light  source  above  the  plane  of  work. 
These  room  proportions  are  classified  in  this  section  by  Room  Index  tables.  The  plane 
of  work,  unless  otherwise  specified  is  ordinarily  considered  to  be  horizontal  and  2J4  feet 
above  the  floor. 

Depreciation  Factor:  This  represents  a  safety  factor  which  provides  added  initial 
illumination  sufficient  to  compensate  for  aeing  of  the  lamps  and  the  falling  off  in  re- 
flecting efficiency  of  the  reflectors,  walls,  and  ceilings  due  to  deterioration  and  the  collection 
of  dust  and  dirt.  A  depreciation  factor  should  always  be  applied  to  the  recommendations 
for  foot-candles  of  illumination  since  these  are  always  stated  in  terms  of  average  service, 
or  sustained  illumination. 

14 


varies  rather  widely  depending  on  the  conditions  in  any  par- 
ticular installation,  such  as  the  accuracy  of  the  operation  and 
fineness  of  detail  to  be  observed,  the  color  of  goods  worked  on 
or  handled  and,  in  the  case  of  stores,  the  advertising  value  re- 
sulting from  the  attractiveness  of  a  well  lighted  interior.  The 
foot-candle  values  recommended  in  the  table  are  the  minimum 
to  .be  adhered  to  if  fully  satisfactory  lighting  is  to  be  assured. 
Under  particular  conditions  considerably  higher  illumination  is 
often  desirable. 

2.  Type  of  Lighting  Unit 

The  selection  of  the  type  of  lighting  unit  depends  not  only 
upon  the  requirements  of  the  work  but  in  some  cases  upon  the 
construction  of  the  room  and  the  color  of  ceiling  and  walls.  For 
example,  semi  and  totally  indirect  lighting  is  unsuited  to  rooms 
with  very  dark  ceilings.  It  is  important  to  specify  the  type  of 
lamp  to  be  used  since,  for  example,  as  shown  in  Table  I,  bowl- 
enameled  lamps  used  in  open  reflectors,  such  as  RLM  standard 
domes,  form  a  much  superior  lighting  unit  from  the  standpoint 
of  glare,  reflected  glare,  and  shadows  than  clear  lamp  units  of 
the  same  type.  In  general,  clear  MAZDA  C  lamps  should  not  be 
used  in  open  reflectors  where  the  mounting  height  is  less  than 
20  feet. 

Factors  other  than  those  listed  in  Table  I  may  enter  into 
the  choice  of  the  lighting  unit  in  certain  instances.  For  example, 
in  stores,  offices  and  other  public  installations,  decorative  effect 
is  often  an  important  item.  The  charts  on  pages  21  and  22 
rate  the  various  types  of  units  comparatively  to  serve  as  a  basis 
for  judgment  of  the  adaptability  of  a  unit  for  a  particular  class 
of  installation. 

3.  Location  of  Outlets,  Mounting  Heigjht,  and  Number  of  Light- 
ing Units 

Make  a  diagram  to  scale  of  the  floor  area  of  the  room.  If 
the  units  are  of  semi  or  totally  indirect  type,  measure  the  ceiling 
height  of  room  and  refer  to  Table  2-b,  page  24,  for  the  permissi- 
ble spacing  of  units  and  preferred  suspension  distance  of  lighting 
units  corresponding  to  this  ceiling  height. 

If  the  units  are  of  direct  lighting  type,  determine  the  mount- 
ing height  and  refer  to  Table  2-a  for  the  permissible  spacing  cor- 
responding to  this  mounting  height.  If  the  units  are  mounted 
as  close  to  the  ceiling  as  possible  (a  minimum  allowance  of  one 
foot  is  usually  necessary  to  provide  for  the  drop  of  the  reflector 

15 


from  the  ceiling),  a  wider  spacing  is  permissible  and  fewer  units 
are  therefore  necessary  for  an  even  distribution  of  light.  Con- 
siderations of  shadows,  appearance  and  arrangement  of  work 
may  make  a  lesser  mounting  height  desirable  even  though  a 
closer  spacing  of  outlets  would  be  needed  to  keep  the  same  uni- 
formity of  illumination.  Ordinarily  lamps  should  not  be  mount- 
ed less  than  10  feet  above  the  floor  unless  a  low  ceiling  makes  it 
necessary. 

Having  determined  the  permissible  spacing  proceed  to  locate 
the  outlets  on  the  diagram  of  the  floor  area.  Locate  the  units  as 
nearly  symmetrically  as  possible  without  appreciably  exceeding 
the  permissible  spacing  for  uniform  illumination.  At  a  greater 
height,  a  spacing  closer  than  that  in  Table  2  results  in  greater 
freedom  from  shadows  but  increases  the  number  of  units  re- 
quired and  makes  the  installation  cost  more.  If  a  spacing  some- 
what closer  than  the  permissible  value  is  adopted,  as  is  often  the 
case,  it  is  allowable,  though  not  necessary,  to  refer  back  to 
Table  2  and  select  a  lower  mounting  height  corresponding  to  the 
new  spacing.  The  distance  between  the  outside  row  of  outlets 
and  the  wall  should  not  exceed  one-half  the  spacing  distance. 
For  office  spaces,  or  where  work  is  carried  on  at  benches  or 
machines  near  the  wall,  this  distance  should  be  approximately 
one-third  the  spacing  distance. 
4.  Lamp  Size 

After  the  outlets  have  been  located  on  the  plan,  the  lamp 
size  to  be  used  may  be  determined  by  the  following  calculation: 

Area  in  Square  Feet  _  Total  Floor  Area  in  Square  Feet 
Per  Outlet  Number  of  Outlets 

Lamp  Lumens    Foot- Candles  x  Depreciation  Factor 

.D  Jxequirea  per  =  ^= — — — ; ; 

Square  Foot  Coefficient  of  Utilization 

Lamp  Lumens       Area  in  Square  Feet        Lamp  Lumens  Required 
C     Required  per  =  ,         per  Outlet  X          per  Square  Foot 

Outlet  (From  A)  (From  B) 

Foot-Candles — Illumination  decided  upon. 

Depreciation  Factor — Safety  factor  or  allowance  for  depreciation  due  to 
aging  of  lamps,  dirt,  dust,  and  deterioration  of  reflecting  value  of  walls. 
Use  1.3  for  fairly  clean  locations.     Use  1.5  for  dirty  locations  or  where 
cleaning  is  infrequent. 

Coefficient  of  Utilization — Proportion  of  the  generated  light  from  the 
lamps  which  reaches  the  plane  of  work.  The  Coefficient  of  Utilization 
for  tlje  jnstajlalion  is  determined  as  follows : 

16 


Table  5,  pages  32  to  35,  shows  that  the  Coefficient  of  Utilization  varies 
according  to  the  type  of  fixture,  the  proportions  of  the  room  expressed  by 
"Room  Index,"  and  the  color  of  the  walls  and  ceiling.  From  the  "Room 
Index"  Table  6,  pages  36  to  42,  find  the  Room  Index  corresponding  most 
nearly  to  the  dimensions  of  the  installation.  Then  the  Coefficient  of 
Utilization  for  the  installation  of  the  type  of  lighting  unit  selected  will 
be  found  from  Table  4,  in  the  proper  column  of  wall  and  ceiling  color 
opposite  the  correct  Room  Index. 

Having  determined  the  lamp  lumens  required  per  outlet  by 
the  above  calculations,  the  wattage  of  MAZDA  lamps  to  be  used 
may  be  found  by  reference  to  Table  7,  page  43,  which  lists  the 
lumen  output  rating  for  each  size  of  MAZDA  and  MAZDA  Daylight 
lamps.  Locate  in  this  table  the  size  of  lamp  of  the  desired  type 
which  most  nearly  meets  the  requirement  of  lumen  output. 
When  the  lamp  lumens  required  fall  nearly  midway  between  two 
sizes,  choose  the  larger  rather  than  the  smaller,  unless  it  is  cer- 
tain that  the  less  illumination  from  the  smaller  will  suffice. 


Computed  Illumination  Values 

The  foot-candles  of  illumination  in  service,  allowing  a  de- 
preciation factor  of  1.3,  obtained  for  systems  having  different 
Coefficients  of  Utilization  and  areas  per  lamp  are  worked  out 
in  Table  8,  pages  44  and  45.  Table  8  can  be  referred  to  as  an 
approximate  check  on  design  computations  made  as  outlined 
above. 

ILLUMINATION  DESIGN  FOR  A  FACTORY  ROOM 

The  floor  plan  of  the  factory  space  to  be  lighted  is  60'  x  120'  as  shown. 

The  work  carried  on  in  the  room  is  assembly  of  sewing  machine  heads. 

Height  of  floor  to  roof  trusses  is  12  feet. 

The  roof  is  of  sawtooth  construction  and  the  walls  and  upper  structure 
are  painted  a  medium  color.  A  considerable  amount  of  dark  material  is  kept 
stacked  along  the  walls  of  the  room. 

Following  the  steps  outlined  on  Pages  14  to  17  the  lighting  design  is  de- 
termined as  follows: 

1.  Foot-Candle  Illumination 

From  Table  4,  Page  27,  8  foot-candles  are  recommended  for  assembly, 
medium  grade. 

2.  Type  of  Lighting  Unit 

Consulting  the  Guide  to  the  Selection  of  Reflecting  Equipment  of  Table  i, 
Page  21,  Unit  No.  2,  the  RLM  dome  with  bowl- enameled  lamp  is  selected 
based  on  efficiency  and  favorable  showing  from  the  standpoints  of  glare, 
reflected  glare,  shadows,  and  maintenance. 

3.  Location  of  Outlets,  Mounting  Height,  and  Number  of  Units 

The  height  of  the  benches  and  therefore  the  plane  of  work  is  3l/2\   above 
the  floor.    The  maximum  mounting  height  of  the  lamps  above  the  floor  is 
n'   (12'  height  from  floor  to  truss  less  i'  allowed  for  reflector  drop). 
Hence,  maximum  mounting  height  of  units  above  plane  of  work  is  n' — 
S1/*    or  7^'. 

17 


From  Tauie  2-a  of  Spacing-Mounting  Height,  Page  23,  a  7^2'  mounting 
height  above  plane  for  direct  lighting  units  is   found  to  indicate  a  per- 
missible spacing  of  approximately  n'  and  since  the  section  of  the  room 
near  the  walls  consists  of  aisles  and  storage,  5^'  may  be  allowed  for  the 
distance  between  the  last  row  of  outlets  and  the  side  walls. 
Reference  to  floor  plan  of  the  room  shows  that  a  id'  spacing  each  way 
(outside  units  5'  from  walls)  would  make  a  symmetrical  layout  in  the  20'  x  30' 
bays  and  this  spacing  is  therefore  adopted.     Outlet  locations   for  the  entire 
space  are  marked  on  the  plan  as  shown  and  72  are  found  to  be  required. 

4.  Lamp  Size 
(A)  Area  in 


Total  Floor  Area  in  Sq    Ft          ?2QO 
Number  of  Outlets  in  Room  '    ~^ 


' 


€.0' 


0          0-f 

a      0 

0       0 

.0        fl 

.0-        .0 

0        A 

'  *  "  ir 

B       H 

0          0 

0         0 

0         0 

0        0 

0         0 

£*       0 

0         0 

0         0 

0         0 

0          0 

^r--=--^--^--| 

.—  M— 

t=-^r===r* 

— 

b»__mi 

fl         K 

0         0 

0           0 

0          0 

.0         0 

$           !0 

8       « 

*     « 

0           « 

0         n 

0          0 

«           t* 

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;    .0        0 

0            0 

0         0 

„      aj 

tt 'Outlet  for  1-150  waU  bowl  enameled  MAZDA  C  lamp  .equipped  with  an  QLM  5t<vndard 
Dome.  Reflector,  wilh  suitable  holder  .Ceflector  localcd  1!  feel  about  the  floor 


5 Foot-Candles  x  Depreciation  Factor    __  8  x  1.30   _  Tg  2 

Square  Foot  Coefficient  of  Utilization  .57 

Area  in  square  feet  per  outlet — 100. 
Foot-Candles — 8. 
Depreciation  Factor — 1.30. 
To  find  Coefficient  of  Utilization. 

From  Room  Index,  Table  6,  page  37,  in  a  room  60'  x  120',  where  the 
mounting  height  of  direct  lighting  units  above  plane  of  work  is  /,  the  Room 
Index  is  5.0  or  from  Page  38  in  the  same  room  where  the  mounting  height  is 
8'  the  Room  Index  is  4.0.  Either  value  might  be  used  for  the  Room  Index 
with  equal  accuracy  as  to  the  result  but  4.0  is  more  conservative. 

Referring  to  Table  5,  Coefficients  of  Utilization,  Page  32,  for  RLM  dome 
bowl-enameled  lamps  in  a  location  with  a  Room  Index  of  4.0  and  where  the 
ceiling  and  walls  are   fairly  dark  the   Coefficient   of   Utilization  is   found  to 
be  .57. 
(C)         Combining  (A)  and  (B) 

Lamp  Lumens  Area  in          Lamp  Lumens 

Required  per  =  Square  Feet   x    Required  per  =  100  x  18.2  =  1820 
Outlet  per  Outlet          Square  Foot 

From  Table  7,  Lumen  Output  of  MAZDA  Lamps,  Page  43,  a  150  watt 
MAZDA  C  lamp  giving  2100  lumens  is  found  to  most  nearly  meet  the  require- 
ment. The  actual  service  illumination  using  this  lamp  will,  of  course,  be 
slightly  greater  than  originally  designed  for,  or 

2100 

x  8  =  9.2  foot-candles 

1820 

18 


As  an  approximate  check  on  the  computation  reference  may  be  made  to 
Table  8  where  with  a  Coefficient  of  Utilization  of  0.55  (the  table  value  nearest 
to  0.57)  and  an  area  per  lamp  of  100  square  feet  the  illumination,  using 
I5o-watt  MAZDA  C  lamps,  is  found  to  be  8.9  foot-candles. 


CHOICE  OF  REFLECTING  EQUIPMENT 

Various  lighting  units  are  rated  in  accordance  with  seven 
fundamentals,  illustrated  on  the  following  page.  The  import- 
ance of  these  criteria  is  different  for  different  classes  of  work. 
It  must  be  emphasized  that  the  relative  importance  of  the  vari- 
ous criteria  should  be  carefully  weighed  with  respect  to  the  par- 
ticular problem  at  hand.  For  instance,  in  an  office  the  criteria 
would  rank  in  importance:  (i)  Direct  glare;  (2)  Reflected  glare; 
(3)  Shadows;  (4)  Efficiency  based  upon  illumination  on  hori- 
zontal; (5)  Maintenance;  (6)  Vertical  illumination.  On  the 
other  hand,  where  lamps  are  to  be  hung  above  a  crane  in  a  foun- 
dry, the  order  of  importance  would  be:  (i)  Efficiency  based 
upon  illumination  on  horizontal;  (2)  Vertical  illumination;  (3) 
Maintenance;  (4)  Shadows;  (5)  Direct  glare;  (6)  Reflected 
glare. 

In  the  chart  the  best  rating  given  is  A-+,  which  denotes  the 
highest  degree  of  excellence,  while  D,  the  lowest,  indicates  that 
an  installation  of  units  so  rated  in  any  particular,  will  very  likely 
prove  unsatisfactory  in  an  installation  where  this  factor  is  im- 
portant. The  ratings  B  and  C  while  indicating  a  result  not  equal 
to  A,  are  decidedly  superior  to  rating  D.  In  other  words  a  rat- 
ing B,  C  +  or  C  in  certain  respects  does  not  disqualify  a  unit 
provided  that  in  the  essential  requirements  of  a  given  location, 
the  unit  is  rated  A  or  B  +• 
A  +  ]  "I  B  +  1  C  + 

A         J.  Excellent      B         S-  Good      C         }.  Fair      D     Very  Bad 
A-  I  V-  C- 


ILLUMINATION  ON  HORIZONTAL  SURFACES  is  a 

prime  requisite  in  offices,  drafting  rooms  and  those  shops 
where  the  problem  is  to  provide  the  best  illumination  for 
sustained  vision  of  flat  surfaces  on  the  horizontal  or  slightly 
oblique  planes  in  which  papers,  books  and  other  flat  ob- 
jects are  usuany  examined. 

ILLUMINATION  ON  VERTICAL  SURFACES  of  work 
or  machine  parts  is  fully  as  important  as  the  lighting 
of  the  surface  in  the  horizontal  plane.  In  a  consideration 
of  the  amount  of  light  necessary  for  factory  illumination, 
the  criterion  must  be  the  intensity  on  all  working  surfaces 
whether  vertical,  horizontal  or  oblique. 


FAVORABLE  APPEARANCE  OF  LIGHTED  ROOM 

refers  only  to  the  general  or  casual  effect  produced  by 
the  complete  system,  and  is  not  intended  to  rate  the  unit 
as  to  satisfaction  from  the  standpoint  of  good  vision  or 
freedom  from  eye  fatigue. 

DIRECT  GLARE  is  the  most  frequent  and  serious 
cause  of  bad  lighting.  It  results  among  other  things  from 
unshaded  or  inadequately  shaded  light  sources  located 
within  the  field  of  vision,  or  from  too  great  contrast  between 
the  bright  light  source  and  a  dark  background  or  adjacent 
surfaces.  Glare  should  be  avoided  by  the  use  of  proper 
reflecting  and  diffusing  equipment. 

REFLECTED  GLARE  from  polished  working  surfaces 
is  particularly  annoying  because  of  the  necessity  of 
directing  the  eyes  toward  those  surfaces,  and  further 
because  the  eyes  are  by  nature  especially  sensitive  to 
light  rays  from  below.  The  harmful  effects  of  this  specular 
reflection  can  be  minimized  by  properly  shielding  from 
below  or  diffusing  the  source. 

SHADOWS,  that  is,  differences  in  brightness  of  sur- 
faces, are  essential  in  observing  objects  in  their  three 
dimensions,  but  are  of  little  or  no  value  in  the  observation 
of  flat  surfaces.  Where  shadows  are  desirable,  they  should 
be  soft  and  luminous,  not  so  sharp  and  dense  as  to  con- 
fuse the  object  with  its  shadow. 

MAINTENANCE  depends  upon  contour  of  reflector, 
construction  of  fixture,  and  condition  of  ceiling.  The 
rating  is  based  upon  the  likelihood  of  breakage,  the 
labor  involved  in  maintaining  the  units  at  comparable 
degrees  of  efficiency,  and  indication  given  of  need  of  clean- 
ing. 


TABLE  1 


A  GUIDE  TO  THE  SELECTION  OF  REFLECTING  EQUIPMENT 

LIGHTING 

UNIT 

EFFICIENCY 

BASED  UPON 

FAVORAILE 

IPPEARANCE  OF 
LIGHTED  ROOM 

DIRECT 
GLARE 

REFLECTED 
GLARE 

SHADOWS 

MAINTENANCE 

ILLUMINATION 
ON  HORIZONTAL 

ILLUMINATION 
ON  VERTICAL 

DIRECT  LIGHTING  PORCELAIN  ENAMEL  REFLECTORS 

1 

R  I  M  DOME 

Jl«^ 

Clear  [.amp, 

90°  to  180°—  0% 
0°  to  90°—  76%i 

A+ 

B+ 

c+ 

C 

D 

c+ 

A+ 

2 

1  I  M  DOME 

Bowl-Enameled  [.amp 

w 

0°,o90°^S6%> 

A- 

B 

B 

B+ 

B 

B+ 

A- 

3 

GLASS  TOP  DOME 

j£k 

Boivl.F-nameled  [.amp 

90°  to  180°—  8%i 
0°to90°-55'/. 

B 

C+ 

A- 

A- 

B 

B+ 

B 

4 

DEEP    BOWL 

A 

Clear  Lamp 

90°  to  180'—  0% 

^5 

r~4^\ 

0°to90°-«5% 

B+ 

B- 

C 

C+ 

D 

C 

A 

5 

DEEP  BOWl 

Bowl-Enameled  Lamp 

0°to90°-S8Sl 

B 

C+ 

C 

B 

C+ 

C+ 

B+ 

3 

FLAT  CONE 

Shielding  Band 

-55 

AK\ 

(r-,90'_54% 

B 

C+ 

C+ 

C-H 

D 

C 

B+ 

7 

FLAT  CONE 

3F 

Clear  Lamp, 

l,y  to  180"—  W-k 
0°  to  90°—  74^1 

B 

B 

C 

D 

D 

C 

A+ 

I 

DIRECT  LIGHTING  OPEN  GLASS  REFLECTORS 

8 

LIGHT  Sin  OPAL 

A 

Clear  Lamp! 

90°  to  180°—  ii'i 
0*  to  90°—  54% 

B+ 

B 

B-f 

C+ 

D 

B- 

B 

9 

LIGHT  DENSITY  OPAL 

Bowl-Enameled  Lamp 

90°  to  180°—  36"* 

^ms 

^W^ 

O'to90°—  »S% 

B 

B- 

A- 

B- 

B- 

B+ 

B~ 

10 

DENSE  OPAL, 

Clear  Lamp 

90°  to  180°—  15".) 

?L5 

0°  to  90°—  67^ 

A+ 

B+ 

C+ 

B 

D 

C+ 

A- 

II 

DENSE  OPAL 

Bowl-Enameled  Lamp 

90°  to  180°—  16%l 

B+ 

B- 

A- 

B+ 

B- 

B 

B 

12 

MIRRORED  GLASS 

Clear  Lamp 

90°  to  180°—  0'* 
0°to90°-68-H 

A 

B 

C 

C+ 

D 

C 

A- 

13 

MIRRORED  GLASS 

Boul-Enameled  Lamp 

90°  to  180°-  0% 

M 

0«  to  90°—  55^ 

B 

C+ 

C 

B- 

C 

C+ 

B- 

(4 

PRISMATIC  NDUSTRIAl 

^^ 

A+ 

A- 

B+ 

C+ 

D 

C+ 

C- 

21 


TABLE  1 


A  GUIDE  TO  THE  SELECTION  OF  REFLECTING  EQUIPMENT 


LIGHTING  UNIT 


EFFICIENCY 

BASED  UPON 


ILLUMINATION     ILLUMINATION 
ON  HORIZONTAL    ON  VERTICAL 


MUDDLE 

IPPEARANCE  OF 
LIGHTED  ROOM 


DIRECT 
GLARE 


REFLECTED 
GLARE 


SHADOWS 


MAINTENANCE 


DIRECT  LIGHTING  ENCLOSING  AND  SEMI-ENCLOSING  UNITS 


15 


TOHF 


B- 


B- 


B- 


B+ 


16 


B+ 


B+ 


SEMI-ENCLOSING 

Compo  Reflector 


19 


A- 


A- 


20 


B+ 


B+ 


A- 


21 


B+ 


B+ 


A- 


SCIN-MDIRECT  AND  INDIRECT  LIGHTING  UNITS 


22 


LIGHT  OPAL 


B- 


C+ 


B+ 


B+ 


A- 


23 


DENSE  OPAL 

(or  Light  Opal  and 
Bowl-Enameled  Lamp) 


c+ 


A+ 


24 


B- 


B+ 


B+ 


25 


ENAMELED 
METAL  REFLECTOR 


c+ 


A+ 


26 


A+ 


MIRRORED  INDIRECT 


27 


28 


C+ 


B+ 


B+ 


A+ 


A+ 


A+ 


A+ 


TABLE  2-a    SPACING— MOUNTING  HEIGHT 
Direct  Lighting  Units,  Including  Semi-enclosing  and  Totally 
Enclosing  Units,  No.  1  to  No.  21 


Mounting  Height 

Permissible  Distance  Between 

of  Unit 

Permissible 

Outlets  and  Sidewalls 

Distance 

Above  Plane 
of  Work 

Above 
Floor* 

Between 
Outlets 

I  n  Usual  Loca- 
tions Where 
Aisles  &  Storage 
Are  Next  to  Wall 

In  Offices  or 
Where  Work 
Benches  are 
Next  to  Wall 

(H) 

(F) 

(D) 

(W) 

(W) 

4 

6^ 

6 

3 

2 

5 

7>£ 

7/4 

31^ 

2>£ 

6 

gi^ 

9 

4X 

3 

7 

914 

iox 

5 

3>4 

8 

iox 

12 

6 

4 

9 

\\y2 

13X 

6J4 

4j^ 

10 

\iy2 

15 

7/4 

5 

11 

13K 

16^ 

8 

5>£ 

12 

14X 

18 

9 

6 

13 

15^ 

19X 

9J4 

6X 

14 

16^ 

21 

10>^ 

7 

15 

17>^ 

22^ 

11 

7K 

16 

18X 

24 

12 

8 

18 

20^ 

27 

13^ 

9 

20 

22^ 

30 

15 

10 

22 

24^ 

33 

16^ 

11 

24 

26X 

36 

18 

12 

27 

29^ 

40X 

20 

13>£ 

30 

32>£ 

45 

22^ 

15 

35 

37^ 

52^ 

26 

17X 

40 

42X 

60 

30 

20 

*Plane  of  work  (P)  assumed  to  be  2  %  feet  above  floor.  When  the  plane  of 
work  is  higher  or  lower  than  2^  feet  above  floor,  neglect  column  (F)  and  work 
from  column  (H). 

**Minimum  allowance  for  (R)  usually  1  foot. 

23 


TABLE  2-b     SPACING— MOUNTING  HEIGHT 
i  and  Totally  Indirect  Lighting  Units,  No.  22  to  No.  28 


Ceiling  Height 

Permissible  Distance 
Between 

Permissible 

Outlet  and  Sidewalls 

Suspension 

Spacing 
Distance 
Between 
Outlets 

In  Usual 
Locations 
Where  Aisles 
and  Storage 

In  Offices 
or  Where 
Work 
Benches  Are 

Distance 
Ceiling  to 
Top  of 
Reflector** 

Above 
Plane  of 

Above 
Floor* 

Work 

Are  Next 

Next  to  Wall 

to  Wall 

(H) 

(C) 

(D) 

(W) 

(W) 

(R) 

5 

7X 

7X 

Zy2 

2X 

IX 

6 

8>£ 

9 

4>£ 

3 

iy* 

7 

9K 

10X 

5 

3X 

ix 

8 

10# 

12 

6 

4 

2 

9 

nx 

13^ 

6>^ 

4>£ 

2X 

10 

12^2 

15 

iy2 

5 

2X 

11 

13JS2 

16^2 

8 

5>£ 

2X 

12 

14>£ 

18 

9 

6 

3 

13 

15X 

19^ 

9^ 

6>^ 

3X 

14 

16X 

21 

10.K 

7 

3}4 

15 

17^ 

22^ 

11 

7X 

3X 

16 

18>£ 

24 

12 

8 

4 

18 

20^ 

27 

13X 

9 

4^ 

21 

23X 

31^ 

15i^ 

10>4 

5X 

24 

26X 

36 

18 

12 

6 

27 

29^ 

40X 

20 

13^ 

6X 

30 

32X 

45 

22^ 

15 

7X 

35 

37^ 

52^ 

26 

17>£ 

8X 

40 

42^ 

60 

30 

20 

n 

T 

P 


\ 


*Plane  of  work  (P)  assumed  to  be  2 K"  feet  above  floor.  When  the  plane  of 
work  is  higher  or  lower  than  2>£  feet  above  floor,  neglect  column  (C)  and  work 
from  column  (H). 

**Suspension  distances  (R)  in  Table  are  based  on  best  distribution  of  light 
and  efficiency  of  utilization  for  standard  units.  In  some  installations  other  con- 
siderations may  require  a  different  suspension  distance. 

24 


TABLE  NO.  3 

Present   Standards   of  Foot- Candles   Illumination  for   Stores, 
Commercial  and  Public  Interiors 

Foot-Candles 

Recommended  Range 

Department  Stores  and  Large  Specialty  Stores 

Main   Floors 10  6-12 

Basement    Store    10  6-12 

Other  Floors    8  5-10 

Show    Windows    .  .  10-100 

Stores  of  Medium  Size 

Clothing,  Dry  Goods,  Furniture,   Etc 8  5-  10 

Exclusive  Small  Stores 

Light    Goods    .* 8  5-  10 

Dark  Goods    12  8-  16 

Small  Stores 

Art 8  5-10 

Automobile    Supply    6  4-    8 

Bake   Shop 6  4-    8 

Book    6  4-    8 

China    6  4-    8 

Cigar     8  5-10 

Clothing    8  5-  10 

Confectionery     8  5-  10 

Dairy  Products   6  4-    8 

Decorator    8  5-  10 

Drug 8  5-10 

Dry  Goods    8  5-  10 

Electrical    Supply    8  5-  10 

Florist    6  4-    8 

Furrier 8  5-  10 

Grocery    6  4-    8 

Haberdashery     8  5-  10 

Hardware 6  4-    8 

Hat    8  5-10 

Jewelry    8  5-10 

Leather,  Handbags  and   Trunks 6  4-     8 

Meat 6  4-    8 

Millinery    8  5-  10 

Music    6  4-    8 

Notions    6  4-    8 

Piano    6  4-    8 

Shoe    8  5-io 

Sporting  Goods   6  4-    8 

Tailor    8  5-10 

Tobacco    8  5-  10 

Variety    Store    10  6-12 

Armories,    Public   Halls 5  3-    6 

Auditoriums     3  2-    4 

Automobile  Show  Room 8  5-  10 

Bank 

Lobby    : 6  4-    8 

Cages   and    Offices 10  6-12 

Barber    Shop    8  5-  10 

Cars 

Baggage     4  3-    6 

Daycoach,   Subway   6  4-     6 

Dining    6  4-    8 

Mail    10  6-12 

Pullman    6  4-    8 

Street  Ry ..  6  4-    8 

25 


TABLE   NO.  3    (Continued) 

Present  Standards  of  Foot-Candles  Illumination  for  Stores, 
Commercial  and  Public  Interiors 

Foot-Candles 
Recommended 

Churches 

Auditorium     3 

Sunday  School  Room 5 

Club   Rooms    4 

Dance    Halls    4 

Dental  Office 

Waiting    Room    4 

Office    .• 15 

Depot — Waiting    4 

Drafting  Room    15 

Elevators — Freight   and  Passenger 4 

Gymnasiums 

Main    Exercising    Floor 8 

Swimming    Pool    4 

Shower  Rooms    4 

Locker    Rooms    4 

Fencing,   Boxing,  Wrestling 8 

Halls,  Passageways  in  Interiors 2 

Hospitals 

Lobby   and   Reception    Room 4 

Corridors    3 

Wards  and             1  with  local  illumination 3 

Private  Rooms      ^{V  non  loc.al  lamination ....  6 

J  night    illumination    o.  I 

Operating  Table   75 

Operating  Room   10 

Laboratories    10 

Hotels 

Lobby     4 

Dining    Room    5 

Kitchen    6 

Bedrooms    6 

Corridors I 

Writing   Room    8 

Indoor  Recreations 

Basketball  and  Indoor   Baseball 10 

Bowling  (On  Alley,  Runway  and  Seats) 5 

(On   Pins)    15 

Billiards  (General)     4 

(On  Table)    15 

Racquet,  Handball,  Squash  and  Indoor  Tennis...  15 

Skating  Rinks    5 

Library 

Reading    Rooms    8 

Stack  Room   4 

Lodge  Rooms  4 

Lunch   Room    8 

Market    8 

Moving  Picture  Theatre 

During   Intermission    3 

During  Pictures    o.  i 

Museum  (General)     5 

(On  Walls)    8 


Range 

2-  4 

3-  6 

3~  £ 

3-  6 

3-  6 

10-  20 

3-  6 

10-  20 

3-  6 

5-  10 

3-  6 

3-  6 

3-  6 

5-  10 

i-  4 


3-  6 
2-    4 

2-  4 

4-  8 

O.I-O.2 
50-100 

6-  12 

6-  12 

3-  6 

4-  8 
4-  8 

4-  8 

1-  2 

5-  10 

6-  12 

3-  6 

10-  20 

3-  6 
10-  20 

10-  20 

4-  8 

5-  10 
3-  6 

3-  6 
5-  10 
5-  10 

2-  4 

O. 1-0.2 

4-  8 

5-  10 


26 


6-  12 

6-  12 

3-  6 

6-  12 


TABLE  NO.  3  (Continued) 

Present  Standards  of  Foot-Candles  Illumination  for  Stores, 
Commercial  and  Public  Interiors 

Foot-Candles 

Recommended  Range 

Office  Buildings 

General   Office   10 

Private    Offices    10 

File  Room.  . .  \ 4 

Stenographer  and  Bookkeeping  Rooms 10 

Vault     4 

Restaurants    5 

Schools 

Auditorium    5 

Class  Rooms,  Library,  and  Office 8 

Corridors   and    Stairways 3 

Drawing    15 

Laboratories     10 

Manual   Training    10 

Sewing  Rooms    15 

Study  Room 

Desks    8 

Blackboards    6 

Studio 

Art  and   Photographic 10 

Moving    Picture — General    5 

— Sets     (Photographic    Daylight)  ..               500-2000 

Telephone 

Manual    Exchanges    5                    3- 

Automatic  Exchanges    10                    6- 

Theatres 

Auditorium    4                x  3- 

Foyer    5                   3- 

Lobby    5- 

Toilet  and  Washrooms 5                    3- 


4-  8 

5-  10 
2-  4 

10-  20 

6-  12 

6-  12 

IO-  20 


10 


6 

12 

6 
6 

TO 


Foot-Candles 
Recommended 


TABLE  NO.  4 
Present  Standards  of  Foot-Candles  Illumination  for  Industrial  Interiors 

Range 

Offices 

Private,   General    10  6-12 

Drafting  Room   15  10-20 

Industrial 

Aisles,  Stairways,   Passageways  and  Corridors....  2  1-2 

Assembling 

Rough    5  3-6 

Medium    8  5-10 

Fine    10  8-16 

Extra   Fine    10-50  

Automobile  Storage  3  2~  4 

Bakeries     8  5-10 

Boilers,  Engine  Rooms  and  Power  Houses 

Boilers,  Coal  and  Ash  Handling,  Storage  Battery 

Rooms     3  2-4 

Auxiliary    Equipment,    Oil    Switches    and    Trans- 
formers      5  3-6 

Switch     Boards,     Engines,     Generators,     Blowers, 

Compressors    6  4-8 


27 


TABLE  NO.  4  (Continued) 
Present  Standards  of  Foot-Candles  Illumination  for  Industrial  Interiors 

Foot-Candles 

Recommended  Range 
Book  Binding 

Folding,  Assembling,   Pasting,    etc 5                    3-6 

Cutting,  Punching,  and  Stitching 8                    5-10 

Embossing    10                   8-12 

Candy   Making    8                    5-10 

Canning   and   Preserving 8                    5-10 

Chemical  Works 

Hand  Furnaces,  Boiling  Tanks,  Stationary  Driers, 

Stationary  or  Gravity  Crystallizing 3                    2-4 

Mechanical  Furnaces,  Generator  and  Stills,  Me- 
chanical Driers,  Evaporators,  Filtration,  Mechan- 
ical Crystallizing,  Bleaching 4  3-6 

Tanks  for  Cooking,  Extractors,  Percolators,  Nitra- 

tors,  Electrolytic  Cells 6                   4-8 

Clay  Products  and  Cements 

-Grinding,  Filter  Pressing,  Kiln  Rooms 3                   2-4 

Molding,  Pressing,  Cleaning  and  Trimming 5                    3~  6 

Enamelling    6                    4-8 

Coloring  and  Glazing 10                   6-12 

Cloth  Products 

Cutting,  Inspecting,  Sewing 

Light  Goods  10  6-12 

Dark  Goods   20  10-50 

Pressing,  Cloth  Treating  (Oil  Cloth,  etc.) 

Light  Goods   8  5-10 

Dark  Goods   12  8-16 

Coal   Breaking  &  Washing,  Screening 3  2-4 

Construction — Indoor  General    3  2-4 

Dairy  Products   6  5-10 

Electric  Manufacturing 

Storage  Battery,  Molding  of  Grids,  Charging  Room,  6  4-8 
Coil  and  Armature  Winding,  Mica  Working,  In- 
sulating   Processes    10  8-16 

Elevator,  Freight  and  Passenger 5  3-6 

Engraving   20  10-50 

Forge  Shops  and  Welding 

Rough  Forging 6  4-8 

Fine  Forging  and  Welding 10  6-12 

Foundries 

Charging  Floor,  Tumbling,  Cleaning,  Pouring*  and 
Shaking  Out*  5  3-6 

*  Since  Pouring  and  Shaking  Out  are  carried  on  in  the  same  location  as 
either  Rough  or  Fine  Molding,  different  illumination  levels  may  be  secured 
for  these  operations  by  cutting  out  some  of  the  lighting  circuits  when  space 
is  used  for  the  former. 

Rough    Molding   and    Core    Making 6                    4-8 

Fine  Molding  and  Core  Making 10                   6-12 

Glass  Works 

Mix  and  Furnace  Rooms,  Pressing  and  Lehr,  Glass 

Blowing  Machines   8                    5-10 

Grinding,  Cutting  Glass  to  Size,  Silvering 8                   5-10 

Fine    Grinding,    Polishing,     Beveling,    Inspection, 

Etching   and   Decorating 10                   6-12 

Glass  Cutting  (Cut  Glass),  Inspecting  Fine 10-50 

28 


TABLE  NO.  4  (Continued) 
Present  Standards  of  Foot-  Candles  Illumination  for  Industrial  Interiors 


Foot-Candles 
Recommended 


Range 


Glove  Manufacturing 
Light  'Goods 

Cutting,    Pressing,    Knitting  .....................  g  5-10 

Sorting,  Stitching,  Trimming  and  Inspecting....  10  8-16 

Dark  Goods 

Cutting,    Pressing,    Knitting  ....................  IO  g_I2 

Sorting,  Stitching,  Trimming  and  Inspecting.  ...  20  10-50 

Hat  Manufacturing 

Dyeing,  Stiffening,  Braiding,  Cleaning  and  Refining 
^ght    .................................  .......  6  4_8 

Dark     .....  .......  ............................  10  6-12 

Forming.    Sizing,    Pouncing,    Flanging,    Finishing, 

Ironing 
Light    ........................................  8  5-10 

'Dark   .........................................  10  6-12 

bewmg 

Light    ........................................  10                  8-16 

Dark   .........................................  IO_5o 

ice  Making 

Engine  and  Compressor  Room  ...................  6                    4-8 

Inspecting 

Rough    ...........................................  6                   4_  8 

Medium     .......................................  10                   6-12 

Fine    ............................................  IS  10-20 

Extra  Fine  ................................  .....  10-50 

Jewelry   and   Watch    Manufacturing  ..................  10-50 

Laundries  and  Dry  Cleaning  ..........................  8                    5-10 

Leather  Manufacturing 

Vats    .........  .  .................................  3                    2-4 

Cleaning,    Tanning   and    Stretching  ................  4                    3-6 

Cutting,  Fleshing  and  Stuffing  ....................  6                    4-8 

Finishing   and    Scarfing  ..........................  10                    6-12 

Leathing  Working 

Pressing  and  Winding 

Light    ........................................  8                   5-10 

Dark    ........................................  10                   6-12 

Grading,  Matching,  Cutting,  Scarfing,  Sewing 

Light     ...........................  .............  10                   8-16 

Dark   ....................................  .  ____  10-50 

Locker   Rooms    .....................................  4  2-4 

Machine  Shops 

Rough  Bench  and  Machine  Work  .....  ............  6  4-8 

Medium  Bench  and  Machine  Work,  Ordinary  Au- 
tomatic Machines,  Rough  Grinding,  Medium  Buf- 
fing   and    Polishing  ............................  10  6-12 

Fine   Bench   and  Machine  Work,   Fine  Automatic 
Machines,   Medium   Grinding,   Fine   Buffing  and 
Polishing   .....................................  12  8-16 

Extra  Fine   Bench  and  Machine  Work,   Grinding 

(fine  work)    ..................................          10-50 

Meat  Packing 

Slaughtering     ...................................  5  3-6 

Cleaning,    Cutting,    Cooking,    Grinding,    Canning, 
Packing    ......................................  8  5-10 


29 


TABLE  NO.  4  (Continued) 
Present  Standards  of  Foot-Candles  Illumination  for  Industrial  Interiors 

Foot-Candles 
Recommended  Range 

Milling  and  Grain  Foods 

Cleaning,  Grinding  or  Rolling 5  3-6 

Baking  or  Roasting  8  5-10 

Flour    Grading    16  10-20 

Packing 

Crating  4  3-6 

Boxing   6  4-8 

Paint   Manufacturing    6  4-8 

Paint  Shops 

Dipping,  Spraying,  Firing 5  3-6 

Rubbing,  Ordinary  Hand  Painting  and  Finishing.  .  8  5-10 

Fine  Hand  Painting  and  Finishing 10  8-16 

Extra  Fine  Hand  Painting  and  Finishing 

(Automobile  Bodies,  Piano  Cases,  etc.) 15  10-50 

Paper  Box  Manufacturing 

Light 6  48 

Dark 8  5  10 

Storage  of   Stock 3  2-4 

Paper  Manufacturing 

Beaters,    Machine,    Grinding 4  3-6 

Calendaring    6  4-8 

Finishing,  Cutting  and  Trimming 8  6-12 

Plating   5  3-6 

Polishing  and  Burnishing 8  5-10 

Printing  Industries 

Matrixing   and    Casting,    Miscellaneous    Machines, 

Presses   8  5-10 

Proof   Reading,  Lithographing,   Electrotyping 10  6-12 

Linotype,  Monotype,  Typesetting,  Imposing  Stone, 

Engraving    10-50 

Receiving    and    Shipping 4  3-6 

Rubber  Manufacturing  and  Products 

Calendars,  Compounding  Mills,  Fabric  Preparation, 
Stock  Cutting,  Tubing  Machines,  Solid  Tire  Op- 
erations, Mechanical  Goods  Building,  Vulcanizing  8  5  10 
Bead  Building,  Pneumatic  Tire  Building  and  Fin- 
ishing, Inner  Tube  Operation,  Mechanical  Goods 
Trimming,  Treading  10  6-12 

Sheet  Metal  Works 

Miscellaneous  Machines,  Ordinary  Bench  Work.  . .  8  5-10 

Punches,  Presses,  Shears,  Stamps,  Welders,  Spin- 
ning,  Fine   Bench   Work 10  8-16 

Tin  Plate  Inspection  10  6-12 

Shoe  Manufacturing 

Hand  Turning,  Miscellaneous  Bench  and  Machine 
Work 8  5-10 

Inspecting    and    Sorting    Raw    Material,    Cutting, 
Lasting  and   Welding    (light) 10  6-12 

Inspecting    and    Sorting    Raw    Material,    Cutting, 

Stitching    (dark)    10-50 

Soap  Manufacturing 

Kettle  Houses,  Cutting,  Soap  Chip  and  Powder...  5  3-6 

Stamping,    Wrapping    and    Packing,    Filling    and 
Packing  Soap  Powder 6  4-8 

30 


TABLE  NO.  4  (Continued) 
Present  Standards  of  Foot-Candles  Illumination  for  Industrial  Interiors 

Foot-Candles 
Recommended  Range 

Steel  and  Iron  Mills,  Bar,  Sheet  and  Wire  Products 

Soaking  Pits  and  Reheating  Furnaces 3  2-4 

Charging  and  Casting  Floors ; 5  3-6 

Muck    and    Heavy    Rolling,    Shearing,    rough    by 

gauge,   Pickling  and  Cleaning 6  4-8 

Plate  Inspection    10  6-12 

Automatic  Machines,  Rod,  Light  and  Cold  Rolling, 

Wire  Drawing,  Shearing,  fine  by  line 8  5-10 

Stone  Crushing  and  Screening 

Belt  Conveyor  Tubes,  Maine  Line  Shafting  Spaces, 

Chute  Rooms,  Inside  of  Bins 2  1-2 

Primary  Breaker  Room,  Auxiliary  Breakers  under 

Bins    ...• 3  2-4 

Screen  Roms 5  3-6 

Store  and  Stock  Rooms 

Rough    3  2-4 

Medium   6  4-8 

Structural    Steel    Fabrication 6  4-8 

Sugar  Grading    16  10-20 

Telephone 

Manual   Exchanges    5  3-6 

Automatic    Exchanges    10  6-12 

Testing 

Rough    5  3-6 

Fine    10  6-12 

Extra  Fine  Instruments,   Scales,  etc 20  10-50 

Textile  Mills 
(Cotton) 
Opening  and  Lapping,  Carding,  Drawing,  Frame 

Roving,  Dyeing 5  3-6 

Spooling,  Spinning,  Drawing  in,  Warping.  Weav- 
ing,   Quilling,    Inspecting,    Knitting,    Slashing 

(over  beam  end) 8  5-10 

(Silk) 

Winding,    Throwing,    Dyeing 12  8-16 

Quilling,  Warping,  Weaving  and  Finishing 

Light  Goods   8  .S-io 

Dark  Goods   10  8-16 

(Woolen) 

Carding,  Picking,  Washing  and  Combing 4  3-6 

Twisting  and   Dyeing 6  4-8 

Drawing  in,  Warping 

Light  Goods  6  4-8 

Dark  Goods  10  8-16 

Weaving 

Light  Goods  8  5-10 

Dark  Goods   12  10-20 

Knitting  Machine  TO  6-12 

Tobacco   Products    5-™ 

Toilet  and  Wash  Rooms 4  3-6 

Warehouse    2  1-2 

Wood  Working 

Rough  Sawing  and  Bench  Work 5  3-6 

Sizing,  Planing,  Rough  Sanding,  Medium  Machine 

and  Bench  Work,  Gluing.  Veneering,   Cooperage  5-io 

Fine  Bench  and  Machine  Working,  Fine  Sanding 
and  Finishing 6-12 

31 


TABLE    5.      COEFFICIENTS   OF    UTILIZATION 

Find   Rocm   Index,   from    Table    6. 

DIRECT  LIGHTING  PORCELAIN  ENAMEL  REFLECTORS 


COLOR 
REFLECTION 
FACTOR 

CEILING 

VERY  LKHT  (70%) 

FAIRLY  LIGHT  (50%) 

FAIRLY  BARK  (30%) 

WALLS 

FAIRLY 
LIGHT  (50%) 

FAIRLY 

DARK  (30%) 

VERY 
DARK  (10%) 

FAIRLY 
LIGHT  (50%) 

FAIRLY 

DARK  (30%) 

VERY 

DARK  (10%) 

FAIRLY 

DARK  (30%) 

VERY 
DARK  (10%) 

REFLECTOR 
TYPE 

ROOM 
INDEX 

COEFFICIENTS  OF  UTILIZATION 

1 

R  I  M  DOME 

^k 

Clear  Lamp 
90°tol8p°-«% 

0°to90°-76% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.34 
.42 
.46 
.50 
.53 

.58 
.62 
.64 
.67 
.69 

.29 
.38 
.43 
.47 
50 

.55 
.59 
.61 
.65 
.67 

.24 
.34 
.39 

.43 
.46 

.51 
.56 
.58 
.63 
.65 

34, 
.42 
.45 
.49 
.52 

.57 
.61 
.63 
.66 
.67 

.29 
.37 
.42 
.46 
.49 

.54 
.58 
.60 
.64 
.66 

.24 
.33 
.39 
.43 
.46 

.51 
.56 
.58 
.62 
.64 

.28 
'.37 
.42 

.45 
.48 

53 
58 
.60 
.63 
.65 

.24 
.33 
.39 
.42 

.45 

51 
56 
.58 
.61 
.63 

2 

RIM  DOME 

^Afct 

jiiiJKik. 

Bowl-Enameled  Lamp 
0°to90°-66% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.32 
.40 

.43 
.46 
.48 

.52 
36 
.57 
.60 
.61 

.28 
.36 
.39 
.43 
.45 

.50 
.54 
.55 
.58 
.59 

.25 
.34 
.37 
.41 
.43 

.48 
.52 
.53 
.56 
.57 

.32 
.39 
.42 
.45 

.47 

.51 

.55 
.56 
.59 
.60 

.28 
.35 
.39 
.43 

.45 

.49 
.53 
.54 
.57 

.58 

.25 
.33 
.37 
.41 
.43 

.47 
.51 
.52 
.55 

.57 

.27 
.35 
.39 

.43 
.45 

.49 
53 
54 

57 
.58 

.25 
.33 
.37 
.41 
.43 

.47 
.51 
.52 
55 
.56 

3 

GLASS  TOP  DOME 

jnHHtL 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.28 
.34 
.38 
.41 
.43 

.47 
.50 
.51 

.53 

.55 

.25 
.31 
.35 
.38 
.40 

.44 
.47 
.49 
.51 
.53 

.22 
.29 
.33 
.36 
.38 

.42 
.45 
.47 
.50 
.51 

.27 
.33 
.36 
.39 
.41 

*5 

.48 
.49 
.51 
.52 

.24 
.30 
.34 

.37 
.39 

.43 
.46 
.47 
.49 

.50 

.22 
.28 
.32 
.35 
.37 

.41 
.44 
.46 
.48 
.49 

.23 
.30 
.33 
.36 

.38 

.41 
.44 
.46 
.48 
.49 

.21 
.28 
.32 
.35 
.37 

.40 
.43 
.45 
.47 

.48 

Bowl-Enameled  Lamp 
90"  to  180°—  8% 

0°to90°-55% 

4 

DEEP  BOWL 

Clear  Cm* 
90°  to  180°—  0% 

0°to90°-65% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 

5.0 

.31 
.38 
.41 
.44 
.47 

.51 
.54 
.56 
.58 
.60 

.26 
.34 
.38 
.41 
.44 

.48 
.51 
.54 
.56 
.58 

.23 
.31 
.35 
.38 
.41 

.45 
.49 
.51 

.54 
.56 

.30 
.37 
.41 
.44 
.46 

.50 
.53 
.55 

.57 
.58 

.26 
.34 
.38 
.41 
.43 

.47 
.51 

.53 
.55 
.57 

.23 
.31 
.35 
.38 
.41 

.45 
.49 
.51 
.54 

.55 

.25 
.33 
.37 
.40 
.43 

.47 
.51 
.53 
55 
.56 

.23 
.31 
.35 
.38 
.41 

.45 
.49 
.51 
.53 

.55 

5 

90°  tol80°--0% 
0°  to  90°—  58% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.29 
.35 
.38 
.41 
.44 

.47 
.50 
.51 
.53 
.54 

.26 
.33 
.36 
.39 
.41 

.45 
.48 
.49 
.51 

.52 

.23 
.31 
.34 
.37 
.39 

.43 
.46 
.47 
.50 
.51 

.29 
.35 
.38 
.41 
.43 

.46 
.49 
.50 

.52 
.53 

.26 
.32 
.36 
.39 
.41 

.44 

.47 
.48 
.50 

.51 

.23 
.30 
.34 
.37 
.39 

.43 
.46 
.47 
.49 

.50 

.25 
.32 
.35 
.38 
.40 

.43 
.46 
.47 
.49 
.50 

.23 
.30 
.34 
.37 
.39 

.43 
.46 
.47 
.49 
.49 

6 

FLAT  CONE 

Shielding  Band 

9Q''tol80''-l% 
0°  to  90°—  54". 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.27 
.32 
.35 
.38 
.40 

.43 
.46 
.47 
.49 
.50 

.23 
.30 
.33 
.36 

.38 

.41 
.44 
.45 
.47 
.48 

.21 
.28 
.31 
.34 
.36 

.39 
.42 
.43 
.46 

.47 

.26 
.32 
.35 
.37 
.39 

.42 
.45 
.46 
.48 
.49 

.23 
.29 

i 

.41 
,43 

.44 
.46 

.47 

.21 
.27 
.31 
.34 
.36 

.39 
.42 
.43 
.45 

.46 

.23 
29 
.32 
.35 

.37 

.40 
.43 
.44 
.46 
.47 

.21 
27 
.31 
.34 
.36 

.39 
.42 
.43 
.45 

.46 

7 

FLAT  CONE 

Clear  Lamp 
90°  to  180°—  10% 

0°to90°—  74% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.26 
.32 
.36 
.41 
.44 

.50 
54 
.57 
.62 
.65 

.20 
.26 
.30 
.35 
.38 

.44 
.48 
.51 
.56 
.60 

.16 
.22 
.26 
.30 
.33 

.38 
.42 
.46 
.51 
.54 

.26 
.32 
.36 
.39 

.42 

.48 
.52 
.55 
.60 
.62 

.19 
.26 
.30 
.34 

.37 

.43 
.47 
.50 
.54 
.56 

.16 
.22 
.26 
.30 
.33 

.38 
.42 
.45 
.50 

.53 

.19 
.26 
.30 
.33 
.36 

.42 
.46 
.49 
53 
.55 

.16 
'    .22 
.26 
.30 
.33 

.38 
.42 
.45 
.50 
.53 

TABLE    5.      COEFFICIENTS   OF   UTILIZATION 

Find   Room  Index   from    Table    6. 

DIRECT  LIGHTING  OPEN  GLASS  REFLECTORS 


COLOR               CEILING 

VERY  LIGHT  00%) 

FAIRLY  LIGHT  (50%) 

FAIRLY  DARK  (30%) 

REFLECTION 

FAIRLY 

FAIRLY 

VERY 

FAIRLY 

FAIRLY 

VERY 

FAIRLY 

VERY 

FACTOR 

LIGHT  (50%) 

DARK  (30%) 

DARK  00%) 

LIGHT  (50%) 

DARK  (30%) 

DARK  (10%) 

DARK  (30%) 

DARK  (10%) 

REFLECTOR 
nPE 

ROOM 
INDEX 

COEFFICIENTS  OF  UTILIZATION 

LIGHT  DENSITY  OPAL 

0.6 

.26 

.21 

.17 

.24 

.19 

.16 

.18 

.15 

J.    x^ 

0.8 

32 

.27 

.23 

30 

.25 

.22 

.24 

.21 

ff       1m 

1.0 

36 

31 

.27 

34 

.29 

.26 

.27 

.24 

//                \\»|i 

1.25 

.40 

35 

.31 

37 

.32 

.29 

30 

.27 

. 

Clear  Lamp 

1.5 

.44 

38 

.34 

.40 

35 

32 

32 

30 

0 

90°tol80°-33% 

2.0 

.49 

.44 

.39 

.45 

.40 

.37 

37 

.34 

XU.// 

25 

.53 

.48 

.44 

.49 

.44 

.41 

.40 

38 

]U|^[    • 

3.0 

.56 

51 

.47 

.51 

.46 

.43 

.42 

.40 

-^<\\^- 

4.0 

.60 

.55 

.51 

.55 

.50 

.47 

.46 

.44 

0°  to  90'—  54% 

5.0 

.62 

58 

.54 

.57 

.53 

.50 

.48 

.46 

LIGHT  DENSITY  OPAL 

0.6 

.22 

.17 

.14 

.20 

.16 

.13 

.14 

.12 

y^v 

0.8 

.27 

.22 

.19 

.25 

.21 

.18 

.19 

.16 

w     ^\\!^ 

1.0 

31 

.26 

.23 

.28     . 

.24 

.21 

.22 

.19 

/«/        *\ 

1.25 

35 

.30 

.26 

31 

.27 

.24 

.24 

.22 

q 

Bow'-Enameled  Lamp 

1.5 

38 

33 

.29 

34 

30 

.26 

.27 

.24 

• 

90°  to  180°—  36% 

2.0 

.43 

38 

34 

38 

34 

.31 

30 

.28 

^S^^f^ 

25 

.47 

.42 

38 

.42 

38 

34 

34 

31 

~~^,,^~~ 

3.0 

»49 

.44 

.40 

.44 

.40 

37 

36 

.33 

^/TN^" 

4.0 

53 

.49 

.45 

.48 

.44 

.41 

39 

37 

0°to90°-^»5% 

5.0 

.56 

52 

.43 

.50 

.46 

.43 

.40 

.39 

0.6 

32 

.27 

.23 

31 

.26 

.22 

.25 

.22 

0.8 

.40 

35 

31 

.38 

34 

31 

33 

.30 

1.0 

.44 

39 

.36 

.42 

38 

35 

37 

35 

1.25 

.47 

.43 

.40 

.46 

.42 

39 

.40 

38 

15 

51 

.47 

.43 

.49 

.45 

.42 

.43 

.41 

10 

90°tol80°-15% 

2.0 

.56 

.52 

.48 

.54 

.50 

.47 

.48 

.46 

•>^|^v 

2.5 

.60 

.56 

.53 

.57 

.54 

52 

.52 

.50 

"\/\  \^" 

3.0 

.63 

59 

55 

.60 

.56 

.54 

.54 

.52 

/T"^\ 

4.0 

.66 

.63 

.60 

.63 

.60 

58 

.57 

.55 

0°to90°-67% 

5.0 

.67 

.65 

.62 

.65 

.61 

.59 

.59 

.57 

DENSE  OPAL 

0.6 

.29 

.24 

.20 

.28 

.23 

.20 

.22 

.20 

s    \. 

.0.8 

35 

31 

.28 

34 

30 

.27 

.29 

.27 

//       N\V 

1.0 

39 

35 

32 

38 

34 

32 

33 

31 

///        ^a 

1.25 

.43 

39 

36 

.41 

38 

35 

.36 

34 

Bowl-Enamcled  Lamp 

1.5 

.46 

.42 

38 

.44 

.40 

37 

.38 

36 

90°  to  180°—  16% 

2.0 

51 

.47 

.44 

.48 

.45 

.42 

.43 

.41 

—  /^/$%  — 

2.5 

.55 

.51 

.48 

52 

.49 

.46 

.47 

.45 

s\  /  XT** 

3.0 

57 

.54 

.50 

54 

.51 

.48 

.48 

.46 

VIV 

4.0 

.60 

.57 

.54 

57 

.54 

.52 

51 

.50 

0°to90°-60> 

5.0 

.62 

.59 

.56 

.58 

.56 

.54 

.53 

.52 

MIRRORED  GLASS 

0.6 

32 

.27 

.24 

.31 

.27 

.24 

.27 

.24 

dJJUlUht. 

0.8 

39 

35 

32 

39 

.35 

32 

35 

.32 

MMffljj/MMflL 

1.0 

.43 

39 

37 

.42 

39 

37 

39 

37 

1.25 

.46 

.43 

.40 

.46 

.43 

.40 

.42 

.40 

I    M 

CKaTL/lrm> 

15 

.49 

.46 

.43 

.48 

.45 

.43 

.45 

.43 

12 

••» 

90°  to  180°-0% 

2.0 

53 

.50 

.48 

.52 

.50 

.48 

.49 

.48 

>^i^V 

25 

57 

.54 

52 

.56 

.54 

.52 

.53 

.52 

I  .  /  lAi 

3.0 

58 

.56 

.54 

.57 

.55 

.54 

54 

.53 

S^**rv\^ 

4.0 

.61 

.59 

57 

.   .60 

.58 

.56 

.57 

.56 

0°  to  90°-68% 

5.0 

.63 

.61 

.58 

.61 

.59 

.58 

.58 

.57 

0.6 

.26 

.22 

.19 

.25 

.22 

.19 

.21 

.19 

0.8 

32 

.29 

.26 

31 

.28 

.26 

.28 

.26 

1.0 

35 

.32 

30 

34 

.32 

.30 

31 

30 

1.25 

38 

35 

33 

37 

35 

33 

34 

33 

13 

P 

1.5 

.40 

37 

.35 

39 

37 

35 

36 

35 

90°  to  180°—  0% 

2.0 

.43 

.41 

39 

.42 

.40 

39 

.40 

39 

2.5 

.46 

.44 

.42 

.45 

.43 

.42 

.43 

.42 

3.0 

.47 

.46 

.44 

.46 

.45 

.44 

.44 

.43 

4.0 

.49 

.48 

.46 

.48 

.47 

.46 

.46 

.45 

5.0 

.50 

.49 

.47 

•     .49 

.48 

.47 

.47 

.46 

PRISMATIC  INDUSTRIAL 

0.6 

.33 

.26 

.21 

31 

.25 

.21 

.24 

.20 

vO^- 

0.8 

.41 

.35 

30 

39 

33 

.29 

.32 

.29 

^^'ll\\^ 

1.0 

.45 

.40 

35 

.43 

39 

34 

37 

33 

•H/nlim 

1.25 

.50 

.44 

.39 

.47 

.42 

38 

.40 

37 

Jj/ll  III  1  Ul)| 

1.5 

52 

.48 

.43 

.50 

.45 

.42 

.43 

.40 

1  i 

Clear  Lamp 

i^ 

90°  to  180--187. 

2.0 

.58 

.54 

.49 

.56 

51 

.47 

.49 

.46 

>^}X\ 

25 
3.0 

.63 
.66 

59 
.62 

54 

58 

.60 
.63 

.56 
59 

.53 
.56 

.54 
.56 

.51 
54 

y*^^^/      \      \Ss^^^i 

4.0 

.71 

.67 

.63 

.67 

.63 

.61 

.60 

58 

**0'to9V—  73%^ 

5.0 

.73 

,69 

.66 

.69 

.65 

.63 

.62 

.60 

33 


TABLE    5.      COEFFICIENTS    OF    UTILIZATION 

Find    Room   Index,    from    Table    6. 

DIRECT  LIGHTING  ENCLOSING  AND  SEMI-ENCLOSING  UNITS 


COLOR 
REFLECTION 
FACTOR 

CEILING 

VERY  LIGHT  (70%) 

FAIRLY  LIGHT  (50%) 

FAIRLY  DARK  (30%) 

WALLS 

FAIRLY 

LIGHT  (50%) 

FAIRLY 
DARK  (30%) 

VERY 
DARK  (10%) 

FAIRLY 
LIGHT  (50%) 

FAIRLY 
DARK  (30%) 

VERY 
DARK  (10%) 

FAIRLY 

DARK  (30%) 

VERY 

DARK  (10%) 

REFLECTOR 
TYPE 

ROOM 
INDEX 

COEFFICIENTS  OF  UTILIZATION 

15 

DIFFUSING  GLOBE 
LiEhtOpal 

90°tol80°-35% 
.0°.to90°—  «W 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.18 
.22 
.26 
.29 
.32 

.37 
.40 

.43 
.47 
.  .49 

.13 
.17 
.21 
.24 
.27 

.32 
.35 
.38 
.42 
.45 

.10 
.14 
.18 
.21 
.23 

.28 
.31 
.34 
.38 
.41 

.16 
.20 
.23 
.26 
.29 

.32 
.35 
.38 
.41 

.43 

.12 
.16 
.19 
.22 
.24 

.28 
.31 
.33 
.37 
.39 

.10 
.13 
.16 
.19 
.21 

.25 
.28 
.30 
.34 

.36 

.10 
.14 
.17 
.19 
.22 

.25 
.28 
.30 
.33 
.34 

.09 
.12 
.14 
.16 
.19 

.22 
.25 
.27 
.31 

.33 

16 

ONE-PIECE  OPAL 

Flattened  Reflecting 
0°  to  90°—  45% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 

5.0 

.22 
.27 
.31 
.35 
.38 

.42 
.46 
.49 
.53 

.55' 

.17 
.22 
.26 
.30 
.33 

.38 
.41 
.45 
.48 
.51 

.14 
.19 
.23 
.26 
.29 

!33 
.37 
.40 
.44 
.47 

.20 
.25 
.28 
.31 
.34 

i.38 
.41 
.43 
.47 
.49 

.16 
.21 
.24 
.27 
.30 

134 
.37 
.39 
.43 

.45 

.13 

.18 
.21 
.24 
.27 

.31 
.34 
.36 
.40 
.42 

.14 
.19 
.22 
.25 
.27 

.31 
.34 
.36 
.38 
.40 

.12 
U7 
.19 
22 
.24 

.28 
.31 
.33 
.36 
.38 

17 

DIFFUSING  GLOBE 

Large  MetalRefleclor 

V  jjj 

90°tol80°-6% 

^ 

0°  to  90°-58T. 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 

5.0 

.22 
28 
.31 
.34 
.36 

.41 
.44 

.47 
.50 
.52 

.17 
.23 
.26 
.30 
.32 

.37 
.41 
.43 
.47 
.49 

.14 
.20 
.23 
.26 
.29 

.33 
.37 
.39 
.43 
.45 

.22 
.27 
.31 
.33 
.36 

.40 
.43 
.45 
.48 
.50 

.17 
.23 
.26 
.29 
.32 

.36 
.40 
.42 
.45 
.47 

.14 
.19 
.23 
.26 
.28 

.33 
.37 
.39 
.43 
.44 

.17 
.23 
.26 
.29 
.31 

.35 
.39 
.41 
.44 
.46 

.14 
.19 
.23 
.26 
.28 

.32 
.36 
.39 
.42 
.44 

18 

SEMI-ENCLOSING 

Metal  Reflector 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.22 
.28 
.31 
.35 
.38 

.43 
.46 
.49 
.54 
.56 

.17 
.22 
.26 
.30 
.33 

.38 
.41 
.44 
.49 
.51 

.13 
.19 
.23 
.26 

.28 

.33 
.37 
.40 
.44 
.47 

.21 
.26 
.30 
.32 

.36 

.40 
.44 
.46 
.50 
.52 

.16 
.21 
.25 
.28 
.31 

.36 
.39 
.42 
.45 
.47 

.13 
.18 
.22 
.25 

.27 

.32 
.36 
.38 
.42 
.45 

.15 
.21 
.24 

.27 
.30 

.34 
.37 
.40 
.43 
.44 

.13 
.18 
.21 
.24 
.26 

.30 
.34 
.37' 
.40 
.43 

90°tol80°-20% 
0°  to  9V—  56^ 

19 

SEMI-ENCLOSING 

Compo  Reflector 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.24 
.30 
.33 
.37 
.39 

.441 
.48 
.50 
.55 
•57 

.18 
.24 
.28 
.32 
.35 

.40 
.44 
.46 
.51 

.53 

.14 
.21 
.25 
.28 
.31 

.35 
.39 
.42 
.47 
49 

.23 

.29 
.32 
.35 
.38 

.42 
.46 
.48 
.53 
.54 

.18 
.24 
.28 
.31 
.34 

138 
.42 
.44 
.49 
..50 

.14 
.20 
.24 
.27 
.30 

'.34 

.38 
.41 
.45 
.47 

.17 
.23 
.27 
.30 
.32 

.37- 
.41 
.43 
.46 

.48 

.14 
.20 
.24 
.27 
.29 

.34 
.38 
.40 
.44 
.46. 

90°tol80°-13% 
0°  to  90°—  60% 

20 

TWO-PIECE  GLASS 

Opal  Reflector  and 
Enameled  Bowl 

,^=^%l^>x 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 

4.0 
5.0 

.22 
.27 
.30 
.33 
.36 

:44 

.46 

.49 
.51 

.17 
.23 
.26 
.29 
.32 

.37 
.40 
.42 
.45 

.48 

.14 
.20 
.23 
.26 
.29' 

.33 
.36 
.38 
'.42' 
.44 

.21 
.26 
.29 
.32 
.35 

% 

.43 
.47 
.48 

.17 
.22 
.26 
.28 
.31 

.35 
.38 
.40 
.43 
.45 

.14 
.19 
.23 
.26 

.28 

.32 
.35 
.37 
.41 
.43 

.16 
.22 
.25 
.29 
.31 

.34 
.37 
.39 
.42 
.43 

.14 
.19 
.22 
.25 
.27 

.31 
.35 
.37 
.40 
•41 

\y 

90°tol80°-127o 
0°  to  90°—  53% 

21 

ONE-PIECE  GLASS 

Enameled  Reflector 

90°  to  180°-22% 
0«  to  90°—  50% 

0.6 
0.8 
1.0 
1.25 
1.5 

2.0 
2.5 
3.0 
4.0 
5.0 

.22 
.27 
.30 
.34 
.37 

.41 
.44 
.47 
.51 
.53 

.17 
.23 
.26 
.30 
.33 

.37 
.40 
.43 
.47 
.49 

.14 
:20 
.23 
.26 
.29 

.33 
.36 
.39 
.43 
.45 

.21 
.26 
.29 
.32 
.34 

.38 
.41 
.43 
.47 
.48 

.16 
.22 
.25 
.28 
.30 

.34 
.38 
.40 
.44 
.45 

.14 
.19 
.22 
.25 

.27 

.31 
.35 
.37 
.41 
.42 

.15 
.20 
.23 
.26 

.28 

.32 
.35 
.37 
.41 
.42 

.14 
.18 
.21 
.24 
.26 

.30 
.33 

.35 
.39 
.40 

34 


TABLE    5.      COEFFICIENTS   OF    UTILIZATION 

Find    Rocvn,   Index    from    Table    6. 

SEMI-INDIRECT  AND  INDIRECT  LIGHTING  UNITS 


COLOR               ™ 

VERY  LIGHT  (70%) 

FAIRLY  LIGHT  (50%) 

FAIRLY  DARK  (30%) 

•ssr    «• 

FAIRLY 

LIGHT  (50%) 

FAIRLY 
DARK  (30%) 

VERY 
DARK  (10%) 

FAIRLY 
LIGHT  (50%) 

FAIRLY 
DARK  (30%) 

VERY 
DARK  (10%) 

FAIRLY 

DARK  (30%) 

VERY 

DARK  (10%) 

REFLECTOR 
TYPE 

ROOM 
INDEX 

COEFFICIENTS  OF  UTILIZATION 

LIGHT  OPAL 

0.6 

.18 

.14 

.11 

.15 

.12 

.09 

.09 

.07 

y        Y        < 

0.8 

.22 

.18 

.15 

.19 

.15 

.12 

.12 

.10 

v^  —  —  v 

1.0 

.26 

.22 

.18 

.22 

.18 

.15 

.14 

.12 

22 

^^^^X 

1.25 

.30 

.25 

.22 

.25 

.21 

.18 

.16 

.14 

1.5 

.33 

.28 

.24 

.27 

.23 

.20 

.18 

.16 

90°tol80°-60'' 

2.0 

.38 

.33 

.29 

.31 

.27 

.24 

.21 

.19 

2.5 

.41 

.36 

.32 

.34 

.30 

.27 

.24 

.22 

""^^T^^^ 

3.0 

.44 

.39 

.35 

.36 

.32 

.29 

.25 

.23 

jVjQ  • 

4.0 

.49 

.44 

.40 

.40 

.36 

.33 

.28 

.26 

0°  to  90°-25 

5.0 

.51 

.46 

.42 

.42 

.38 

.35 

.29 

.28 

DENSE  OPAL 

0.6 

.16 

.13 

.11 

.12 

.10 

.08 

.07 

.06 

(or  Lieht  Opal  and 

0.8 

.20 

.17 

.15 

.16 

.13 

.11 

.09 

.08 

Bowl-enameled  Lamp) 

1.0 

.23 

.20 

.17 

.18 

.15 

.13 

.10 

.09 

/      ?       \ 

1.25 

.27 

.23 

.20 

.21 

.18 

.16 

.12 

.11 

>^            /Mil 

1.5 

.29 

.26 

.22 

.23 

.19 

.17 

.13 

.12 

^^^     ^^^ 

90°  to  180°—  70?f 

2.0 

.33 

.29 

.26 

.26 

.22 

.20 

.15 

.14 

2.5 

.36 

.32 

.29 

.28 

.25 

.23 

.17 

.16 

^^JA^" 

3.0 

.39 

.35 

.32 

.29 

.27 

.25 

.18 

.17 

^^^Xf^^ 

4.0 

.43 

.39 

.36 

.32 

.30 

.28 

.20 

.19 

0°  to  90°—  10'* 

5.0 

.45 

.41 

.38 

.34 

.32 

.30 

.22 

.20 

ENAMELED 

0.6 

.18 

.15 

.13 

.14 

.12 

.11 

.09 

.08 

METAL  REFLECTOR 

0.8 

.22 

.19 

.17 

.18 

.16 

.14 

.12 

.11 

Opal  Glass  Bottom 

1.0 

.25 

.22 

.20 

.20 

.18 

.16 

.14 

.13 

\\  

1.25 

.29 

.25 

.22 

.23 

.21 

.19 

.15 

.15 

^^i.     ^=^/^~ 

1.5 

.31 

.28 

.25 

.25 

.22 

.20 

.17 

.16 

^    ~_/ 

90°  to  180°—  61% 

2.0 

.34 

.31 

.29 

.28 

.25 

.23 

.19 

.18 

v*\iy~y^ 

2.5 

.37 

.34 

.32 

.30 

.28 

.26 

.21 

.20 

v^sl^x 

3.0 

.39 

.36 

.34 

.31 

.29 

.27 

.21 

.20 

/^fv\ 

4.0 

.43 

.40 

.38 

.34 

.32 

.30 

.23 

.22 

0«to90°—  14% 

5.0 

.45 

.42 

.40 

.36 

.34 

.32 

.25 

.23 

rs 

0.6 

.16 

.13 

.11 

.12 

.10 

.08 

.07 

.06 

._  '  «      I,, 

0.8 

.19 

.16 

.14 

.15 

.13 

.11 

.08 

.08 

^^     ^f 

1.0 

.22 

.19 

.17 

.17 

.15 

.13 

.10 

.09 

Bowl-enameled  Lamp 

1.25 

.25 

.22 

.19 

.20 

.17 

.15 

.11 

.10 

1C 

1.5 

.27 

.24 

.21 

.21 

.18 

.16 

.12 

.11 

25 

90°tol80°-«97. 

2.0 

.31 

.28 

.25 

.24 

.21 

.19 

.14 

.13 

2.5 

.34 

.31 

.28 

.25 

.23 

.22 

.15 

.15 

Vy^<s]^3 

3.0 

.36 

.33 

.31 

.27 

.25 

.23 

.16 

.15 

/^1^^-v 

4.0 

.40 

.37 

.34 

.29 

.28 

.26 

.18 

.17 

0°to90°-67' 

5.0 

.41 

.38 

.37 

.31 

.29 

.28 

.19 

.18 

CLEAR  TOP  ENCLOSED 

0.6 

.16 

.12 

.10 

.13 

.10 

.08 

.07 

.06 

Enameled  Glass 

0.8 

.20 

.16 

.13 

.17 

.13 

.11 

.10 

09 

<r^f/^'^^:^~~~r\ 

1.0 

1  O^ 

.23 
"y(\ 

.19 
oo 

.16 

.19 

,15 

.13 

.12 

.10 

26 

^     ^jf^ 

I.£D 

1.5 

.£O 

.29 

•&£ 

.25 

.19 
.21 

.21 
.24 

.18 
.20 

.15 
.17 

.14 
.15 

.12 
.13 

90°  to  180°-54% 

2.0 

.32 

.28 

.25 

.26 

.23 

.20 

.18 

.16 

\j    / 

2.5 

.36 

.31 

.28 

.29 

.26 

.23 

.20 

.18 

^S^^— 

3.0 

.38 

.34 

.31 

.31 

.28 

.25 

.22 

20 

//^Y\ 

4.0 

.42 

.38 

.35 

.34 

.31 

.29 

.24 

.22 

5.0 

.44 

.40 

.37 

.36 

.33 

.31 

.25 

.24 

MIRRORED  INDIRECT 

0.6 

.15 

.12 

.10 

.11 

.09 

.07 

.05 

.04 

0.8 

.18 

.15 

.13 

.13 

.11 

.09 

.07 

.06 

^^j-^_ 

1.0 

.22 

.19 

.16 

.15 

.13 

.11 

.08 

.07 

xFT 

1.25 

.25 

.22 

.19 

.18 

.15 

.13 

.09 

.08 

AV 

>ix 

1.5 

.27 

.24 

.21 

.20 

.17 

.15 

.10 

.09 

27 

mm 

90"tol80°-805« 

2.0 

.30 

.27 

.25 

.22 

.19 

.17 

.11 

.10 

2.5 

.34 

.31 

.28 

.24 

.22 

.20 

.13 

.12 

CvT/") 

3.0 

.36 

.33 

.30 

.26 

.24 

.22 

.14 

.13 

^^1^-' 

4.0 

.40 

.37 

.34 

.28 

.26 

.24 

.15 

.14 

0°to90°-0r/' 

5.0 

.42 

.39 

.37 

.30 

.28 

.26 

.17 

.15 

ENAMELED 

0.6 

.14 

.11 

.10 

.10 

.08 

.07 

.04 

.04 

METAL  INDIRECT 

0.8 

.17 

.14 

.13 

.13 

.10 

.09 

.06 

.05 

1.0 

.20 

.17 

.15 

.14 

.12 

.10 

.07 

.06 

W-^       ^^    a/ 

1.25 

.23 

.20 

.17 

.17 

.14 

.13 

.08 

.07 

AM 

x^g^je^ 

1.5 

.25 

.22 

.19 

.18 

.15 

.14 

.09 

.08 

yP 

CO 

90°tol80°—  74fr 

2.0 

..28 

.25 

.23 

.21 

.18 

.16 

.10 

.10 

V         I         / 

2.5 

.31 

.28 

.26 

.22 

.20 

.18 

.12 

.11 

P^U^N 

3.0 

.33 

.30 

.28 

.24 

.22 

.20 

.13 

.12 

*^^M^y* 

4.0 

.37 

.34 

.32 

.26 

.24 

.22 

.14 

.13 

rggg^g 

S.O 

.39 

.36 

.34 

.28 

.26 

.24 

.15 

.14 

35 


TABLE  6       ROOM  INDEX 
For    Finding    Coefficient    of    Utilization    from    Table    rj 


Direct  Lighting-sou RCES  4  FEET  ABOVE  WORK  PLANE 


8i 

ROOM  LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

8 
10 
12 
~14~ 

1.0 

1.25 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

1.25 
1.25 

nr 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

1.5 

I7s~ 

1.5 
1.5 

1.5 

1.5 

1.5 
2.0 

2.0 
2.0 

2.0 
2.0 

2.0 
2.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.5 

2.0 

2.5 

2.0 

2.0 

2.5 

2.0 

2.5 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

16 

1.5 

n~ 

1.5 
1.5 
1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

18 
~20~ 
24 

2.0 
2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 
3.0 

3.0 

3.0 

3.0 

3.0 
3.0 

1.5 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

1.5 

2.0 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

30 

"3? 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

sTo~ 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

40 

^5<r 

60 
~70 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

sTo" 

2.0 
2.0 
2.0 

2.0 
2.0 

2.5 
2.5 

2.5 
2.5 

3.0 
3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 
T.O 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

80 
100 

2.0 
2~0~ 

2.0 
2.0 

2.5 
2.5 

2.5 
2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 
5.0 

5.0 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

120 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG  Q  FEET  ABOVE  WORK  PLANE 


Direct  Lighting-sou RCES  5  FEET  ABOVE  WORK  PLANE 


5I 

ROOM    LENGTH—  FEET 

Si 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

s 

"llT 

0.8 

nr 

0.8 
1.0 

1.0 

1.0 

1.0 
1.25 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 
1.5 

1.5 

1.5 

1.5 
1.5 

1.5 
1.5 

1.5 

1.5 
1.5 

1.5 
1.5 

1.5 

T7F 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

12 

1.0 

1.25 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

14 
16 

1.0 
1.25 

1.25 
1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 
2.0 
2.5 

2.0 

2.0 

2.0 

2.0 

2.0 
2.0 

2.0 

2.0 
2.0 

2.0 
2.0 

2.5 

2.0 

1.5 

1.5 
1.5 

1.5 

1.5 

2.0 
2.0 

2.0 
2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

T.T 

18 

1.25 

1.25 

1.5 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

20 
24 

1.25 

1.5 

1.5 
1.5 

1.5 
2.0 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 
3.0 

2.5 

2.5 

2.5 

2.5 

2.5 

1.5 

2.0 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

30 
35 

1.5 
1.5 

1.5 
1.5 

2.0 
2.0 

2.0 
2.0 
2.0 
2.0 
2.0 
2.0 
2.0 
2.0 
2.0 

2.0 

2.5 
2.5 

2.5 

2.5 
2.5 

2.5 
2.5 

3.0 
3.0 

3.0 
3.0 
4.0 
4.0 

3.0 
4.0 
4.0 
4.0 

3.0 

3.0 
4.0 

3.0 
4.0 
4.0 

3.0 
4.0 

3.0 

3.0 
4~(T 

3.0 
4.0 

3.0 

3.0 

4.0 

4.0 

4.0 

40 
~50~ 

1.5 
1.5 

2.0 
2.0 

2.0 
2.0 
2.0 
2.0 
2.0 

2.5 

2TT" 

3.0 
3.0 
3.0 

3.0 
3.0 

4.0 
5.0 

4.0 
5.0 

4.0 
5.0 
5.0 
5.0 

4.0 

sTo~ 

4.0 

4.0 
5.0 
5.0 
5.0 
5.0 

4.0 
5.0 

4.0 

sTo" 

5.0 
5.0 

5.0 

5.0 

60 
70 

1.5 
1.5 

2.0 
2.0 
2.0 

2.5 
2.5 
2.5 
2.5 
2.5 

2.5 
2.5 
2.5 

3.0 
3.0 
3.0 

4.0 
4.0 
4.0 

4.0 
4.0 
4.0 

5.0 

5.0 

5.0 
5.0 
5.0 

5.0 
5.0 

5.0 
5.0 
5.0 

3.0 

5.0 
5.0 

5.0 
5.0 

5.0 

80 

1.5 

3.0 

5.0 

5.0 

5.0 

5.0 

100 
120 

1.5 
1.5 

2.0 

2.0 
2.0 

2.5 

3.0 
3.0 

3.0 

4.0 

4.Q 
4.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

5.0 

5.0 
5.0 

5.0 
5.0 

5.0 
5.0 

2.0 

2.5 

3.0 

4.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG 


FEET  ABOVE  WORK  PLANE 


36 


TABLE  6  ROOM  INDEX 
For  Finding  Coefficient  of  Utilization  from  Table  4 


Direct  Lighting- so  URGES         FEET  ABOVE  WORK  PLANE 


ROOM 
WIDTH 

ROOM    LENGTH—  FEET 

10 

12 

14  1    16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

8 

0.8 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

10 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1   5 

1.5 

1.5 

12 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

14 

1.0 

1.0 

1.25 

1.25 
1.25 

1.25 
1725 

1.25 
1.5 

1.5 
1.5 

1.5 

ITT 

1.5 

nr 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 
2.0 

2.0 
2.0 

2.0 
2.0 

2.0 
2.0 

2.0 
2.0 

16 

1.0 

1.0 

1.25 

2.0 

2.0 

2.0 

2.0 

2.0 

18 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

?.o 

2.0 

20 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 
2.5 

24 
30 

~35~ 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

40 
50 
60 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 
5.0 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

70 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

80 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

100 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

120 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG   Q   FEET  ABOVE  WORK  PLANE 


Direct  Lighting- so  URGES   7  FEET  ABOVE  WORK  PLANE 


]  ROOM  1 
WIDTH 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35  |* 

50 

60 

70   1    80 

100 

120 

140 

170 

200 

8 
10 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 
1.0 

0.8 
1.0 

1.0 
1.0 

1.0 
1.25 

1.0 

1.25 

1.0 
1.25 
1.5 

1.0 

1.25 
1.5 

1.0 

1.0 

1.0 

1.0 

1.0 
1.25 
1.5 

1.   0 

i7o~ 

0.6 
0.8 

0.8 
0.8 
0.8 

0.8 

0.8 

0.8 

0.8 

1.25 
1.5 
ITT 

1.25 
1.5 
1.5 

1.25 
1.5 
ITT 

1.25 

T7T 

12 

0.8 
1.0 

0.8 
1.0 

1.0 
1.0 

1.0 
1.0 

1.0 

1.25 
1.25 

1.25 

1.25 

1.25 

1.5 

1.25 
1.5 
2~7T 

14 
~16 

0.8 
0.8 

1.25 
1.5 

1.5 
1.5 

1.5 

1.5 

1.5 

1.5 

1.5 
2.0 

1.5 

1.5 

1.5 

2.0 

0.8 
1.0 

1.0 
1.0 

1.25 

1.25 

1.25 

2.0 
2.0 

2.0 

27o~ 

2.0 
2.0 

2.0 
2.0 

2.0 
2~0~ 

18 

0.8 

1.25 

1.25 
1.25 

1.25 
1.5 

1.5 
1.5 

1.5 
1.5 

1.5 
1.5 

1.5 
2.0 

2.0 

2.0 

2.0 

2.0 
2.0 

20 

1.0 

1.0 

1.0 

1.25 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

24 

1.0 

1.0 
1.25 

1.25 
1.25 

1.25 
1.5 

1.5 
1.5 
1   5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

2.5 
3.0 

2.5 
3.0 

2.5 
3.0 

2.5 
3.0 

2.5 
3.0 

2.5 
3.0 

2.5 

oO 

1.0 

1.5 
1.5 

2.0 
2.0 

2.0 
2.0 

2.0 
2.5 

2.5 
2.5 

2.5 

2.5 

3.0 

35 

1.0 

1.25 

1.5 

1.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

40 
50 

1.25 
1725 

1.25 
1.5 
1.5 

1.5 
1.5 
1.5 

1.5 
l.S 

2.0 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 
4.0 

3.0 

47b~ 

3.0 
4.0 

3.0 
4.0 

2.0 
2?(T 

2.0 
2.0 

2.0 

2.5 

2.5 
2.5 

3.0 
3.0 

3.0 
3.0 

4.0 
4.0 

4.0 
4.0 

4.0 

4.0 

4.0 

60 

1.25 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

70 

1.25 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

80 

1.25 

1.5 

1.5 

1.5 

2.0 
2~^T 

2.0 
2.0 
2.0 

2.0 

2.5 

3.0 
3.0 
3.0 

3.0 

3.0 
3.0 
3.0 

4.0 

5.0 

5.0 

5.0 

5.0 
5.0 

5.0 

s7(T 

5.0 

s7o~ 
s7b~ 

5.0 
50 

sTo" 

5.0 
5.0 

100 
120 

1.25 

1.5 

2.0 
27b~ 

2.5 
27T 

3.0 
3.0 

4.0 
4.0 

5.0 
5.0 

5.0 

5.0 

1.25 

1.5 

1.5 

2.0 

5.0 

5.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG 


FEET  ABOVE  WORK  PLANE 


37 


TABLE  6      ROOM  INDEX 
For    Finding    Coefficient    of    Utilization    from    Table 


Direct  Lighting-sou RCES  Q  FEET  ABOVE  WORK  PLANE 


1  ROOM  1 
|  WIDTH  I 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

8 
10 

TT 

0.6 
0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

1725 

1.0 
1725 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.25 

1.25 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

14 

T<f 

~18~ 

0.6 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 
2~(T 

0.6 

0.8 

1.0 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

20 
~24 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

30 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

35 
40 
50 
60 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 
3.0 

3.0 
3.0 

3.0 
3.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

1.0 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

4.0 

4.0 

4.0 

4.0 
5.0 

4.0 
5.0 

4.0 

70 
1JO~ 

1.25 

1.25 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 
5.0 

1.25 

1.5 
1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

100 
120 

1.25 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 
5.0 

1.25 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG   "J  2   FEET  ABOVE  WORK  PLANE 


Direct  Lighting-so URGES  Q  FEET  ABOVE  WORK  PLANE 


1  ROOM  1 

|  WIDTH] 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

I  70  j   200 

8 
10 
12 
~14~ 

0.6 

0.6 

0.6 

0.6 
0.6 
0.8 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 
1.0 

1.0 
1.0 

1.0 
1.0 

1.25 

1.0 
1.0 
1.25 

1.0 

0.6 
0.6 
0.6 

0.6 
0.6 

o7<T 

0.6 
0.6 
0.8 

0.6 
0.8 

0.6 
0.8 
0.8 

0.8 
0.8 
1.0 

0.8 
1.0 
1.0 

0.8 
1.0 

1.0 
1.0 
1.0 

1.0 
1.0 

1.25 

1.0 
1.25 
1.25 

1.0 

1.0 

1.0 
1.25 
1.5 

1.25 
1.25 

1.25 
1.5 

1.25 
1.5 

1.25 

0.8 

0.8 

1.0 

1.5 

1.5 

1.5 

16 
18 
~20~ 
24 

0.6 
0.6 
b~6~ 

0.8 
0.8 

oTs" 

0.8 

0.8 
0.8 
0.8 

0.8 
1.0 
1.0 

1.0 
1.0 

1.0 
1.0 
1.0 

1.0 
1.0 

1.25 

1.0 
1.25 
1.25 
1.5 

1.25 
1.25 

1.25 
1.25 
1.5 

1.25 

1.5 
1.5 
1.5 

1.5 
1.5 
1.5 

1.5 

1.5 

1.5 

1.5 
1.5 

1.5 
1.5 

1.5 
1.5 
2.0 

1.5 
1.5 

1.5 
2.0 

1.5 
2.0 
2.0 

1.5 

1.0 

1.25 

2.0 
2.0 

2.0 
2.0 

2.0 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

30 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

35 

0.8 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

2.0 
2.0 

2.0 
2.0 
2~7(T 

2.0 
2.0 
2.5 

2.0 
27T~ 
2.5 

2.5 
2.5 
3.0 

2.5 

2.5 

2.5 

2.5 
3.0 
.0 
4.0 

2.5 
3.0 
3.0 
4.0 
4.0 
5.0 

2.5 
3.0 
3.0 

2.5 

40 
~50~ 
60 
70 
~80~ 

1.0 
1.0 

i7o~ 

1.0 
1.0 

1.25 

1.0 
1.25 
1.25 

1.25 
1.25 
1.5 

1.25 
1.5 
1.5 

1.5 
1.5 
1.5 

1.5 
1.5 
2.0 

2.5 
3.0 

2.5 
3.0 

3.0 
3.0 
4.0 

3.0 
3.0 
4.0 

2.0 
2.0 
2.0 

2.5 
2.5 
2.5 

2.5 
2.5 
2.5 

3.0 
3.0 
.0 

3.0 
3.0 
4.0 

3.0 
4.0 
4.0 

4.0 

4.0 
4.0 
5.0 

1.0 
1.0 

1.25 
1.25 

1.25 
1.5 

1.5 
1.5 

1.5 
1.5 

1.5 
2.0 

2.0 
2.0 

4.0 
4.0 

4.0 
5.0 

4.0 
.0 

4.0 
5.0 

100 

1.0 
1.0 

1.25 

1.5 

1.5 

1.5 
1.5 

2.0 

2To~ 

2.0 
2.0 

2.5 

2.5 

3.0 

.0 

4.0 

4.0 

5.0 
5.0 

5.0 
5.0 

.0 
~0~ 

5.0 

5.0 

5.0 

120 

1.25 

1.5 

1.5 

2.5 

2.5 

3.0 

.0 

4.0 

4.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG 


FEET  ABOVE  WORK  PLANE 


TABLE  6      ROOM  INDEX 
For    Finding    Coefficient    of    Utilization    from    Table    5 


Direct  Lighting-sou RCES  JQ  FEET  ABOVE  WORK  PLANE 


1  ROOM 
WIDTH 

JROOM    LENGTH—  FEET 

10  |    12 

14 

16 

18 

20 

24  1    30 

35 

40 

50  1    60 

70 

80 

100 

120 

140 

170 

200 

8 
10 
12 

0.6 

0.6 
0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

1.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.25 

1.25 

1.25 

14 
~uT 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

18 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

20 
~24~ 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

1.5 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

30 
~35~ 

0.6 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 

2.0 
2.5 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

40 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

2.5 

50 
60 

0.8 
0.8 

1.0 

1.0 
1.25 

1.25 
1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 
3.0 

1.0 

1.25 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

70 
~80~ 

1.0 
1.0 

1.0 
1.25 
1.25 

1.25 
1.25 

1.25 
1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

3.0 

3.0 

3.0 

4.0 

4.0 

4.0 

4.0 

4.0 
4.0 

4.0 
4.0 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

4.0 

4.0 

4.0 

100 

1.0 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

120 

1.0 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiuNG    "]  5   FEET  ABOVE  WORK  PLANE 


Direct  Lighting,  so  URGES  j  2  FEET  ABOVE  WORK  PLANE 


I  ROOM  1 
WIDTH 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

8 



0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 
0.8 

0.8 
0.8 

0.8 
1.0 

0.8 
1.0 

0.8 
1.0 
1.0 

0.8 
1.0 
1.0 

10 
~12~ 
14 
16 
18 

0.6 
0.6 
0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.8 

0.6 
0.6 
0.8 

0.6 
0.6 
0.8 

0.6 

0.8 

0.8 
0.8 

0.8 
1.0 

0.8 
1.0 

1.0 
1.0 

1.0 
1.25 
1.25 
1.25 

1.0 

1.25 
1.25 

1.0 

0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.8 

0.6 

1.25 
1.25 

1.25 
1.25 

1.25 
1.25 
1.5 

0.6 
0.6 

0.8 
0.8 

0.8 
0.8 

0.8 
0.8 

0.8 
1.0 

0.8 
1.0 

1.0 
1.0 

1.0 
1.0 

1.25 

1.25 
1.25 

1.25 
1.25 

0.6 

1.5 

1.5 
1.5 

1.5 

20 
~2^ 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.8 
0.8 

0.8 
0.8 

0.8 
0.8 

0.8 
1.0 

1.0 
1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 
1.5 

1.5 
1.5 
2.0 
2.0 

1.25 
1.25 

1.25 

1.25 

1.5 
1.5 

1.5 
1.5 

1.5 
1.5 

1.5 
2.0 

1.5 
2.0 
2.0 

1.5 
2.0 
2.0 

30 

"sT 

0.6 

0.6 
0.6 

0.8 

0.8 
0.8 

0.8 

1.0 
1.0 

1.0 

1.25 

1.5 

1.5 

2.0 
2.0 

0.6 

0.8 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

40 
50 

^o" 

0.6 

0.6 

0.8 

0.8 

1.0 

1.0 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 
2.5 
2.5 
3.0 

2.0 

2.5 
2.5 

2.5 
2.5 
3.0 

2.5 

2.5 
2.5 
3.0 
3.0 
4.0 

0.6 
0.8 

0.8 
0.8 

0.8 
1.0 
1.0 

1.0 
1.0 

1.0 

1.25 

1.25 
1.5 
1.5 

1.5 
1.5 

1.5 

1.5 
1.5 
2.0 

1.5 
2.0 

2.0 

2.0 
2.5 
2.5 

2.5 
2.5 
3.0 

2.5 

2.5 
3.0 
3.0 

1.0 

1.25 

2.0 

3.0 
3.0 

3.0 

70 
80 
100 
120 

0.8 

0.8 

1.25 
1.25 
1.25 

1.25 

1.25 

2.0 
2.0 
2.0 

2.5 

3.0 
4.0 

3.0 
4.0 

0.8 
0.8 

1.0 
1.0 
1.0 

1.0 

1.25 

1.25 
1.25 

1.25 
1.5 

1.5 
1.5 
1.5 

1.5 
2.0 
2.0 

2.0 
2.0 

2.5 
2.5 

2.5 
3.0 
3.0 

3.0 
3.0 
3.0 

3.0 

4.0 

4.0 

4.0 
4.0 

4.0 

4.0 

4.0 
5.0 

4.0 
5.0 

4.0 
5.0 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

2.5 

2.5 

4.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG    \  Q   FEET  ABOVE  WORK  PLANE 


39 


TABLE  6      ROOM  INDEX 
For    Finding:    Coefficient    of    Utilization    from    Table    5 


Direct  Lighting-sou RCES   ]  4  FEET  ABOVE  WORK  PLANE 


1  ROOM  1 

|  WIDTH) 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

8 
~nT 

0.6 

0.6 

0.6  |o.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

0.8 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

0.8 

0.8 

12 
14 
~16 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

0.8 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

0.8 

1.0 

1.0 
1.0~ 

1.0 
1.0 

1.0 
1.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.0 

18 
20 
24 

0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.8 
0.8 

0.8 
0.8 

0.8 

0.8 

iTo" 

1.0 

1.0 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.25 

0.6 
0.6 

0.8 

1.0 

1.0 

1.25 

1.25 
1.5 

1.25 
15 

1.25 
1.5 

1.25 
1.5 

1.25 
I.I" 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.25 

30 
35 
~40~ 

0.6 

0.6 

0.6 

0.8 

0.8 

oTs" 

0.8 
1.0 

1.0 
1.0 

1.0 

1.25 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 
2.0 
2.0 

7.0 
2.0 
2.0 

2.0 
2.0 
2.0 

0.6 
0.6 

0.6 

1.25 

1.5 

1.5 

1.5 
1.5 

1.5 
2.0 

2.0 
2.0 

2.0 
2.0 

0.6 

0.6 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

50 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.25 

1.5 

1.5 

.0 

2.0 

2.0 

2.0 

2.5 

2.5 

2.5 

2.5 

2.5 

60 
70 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

.0 

2.0 

2.0 

2.5 

2.5 

2.5 

3.0 

3.0 

3.0 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.5 

1.5 

1.5 

.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

3.0 

80 

0.8 

0.8 
0.8 

0.8 
0.8 
1.0 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 
4.0 

3.0 
4.0 

3.0 
4.0 

100 

0.8 

1.0 

1.0 

1.25 

1.5 

1.5 

2.0 

2.0 

.5 

2.5 

3.0 

3.0 

4.0 

4.0 

120 

0.8 

0.8 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

2.0 

.5 

2.5 

3.0 

3.0 

4.0 

4.0 

5.0 

5.0 

5.0 

Semi  and  Indirect  Lighting-CEiLiNG  2  1    FEET  ABOVE  WORK  PLANE 


Direct  Lighting-sou RCES  1  Q  FEET  ABOVE  WORK  PLANE 


I  ROOM 
1  WIDTH 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

2CO 

8 

~To~ 





0.6 

0.6 
0.6 
0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 

0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.8 

0.8 

0.8 

0.8 

0.8 





0.6 

o7<r 

0.6 

0.6 
0.6 

0.8 

0.8 

0.8 
1.0 

12 
14 

~i<r 

~18~ 
20 

~zT 

~3<r 

35 
40 
~50~ 



0.6 

0.6 
0.6 
0.6 

0.6 
0.6 

0.6 
0.8 
0.8 

0.8 
0.8 
0.8 

0.8 
0.8 
1.0 

0.8 

0.8 

1.0 

0.6 

0.6 

0.6 
0.6 
0.6 

0.6 
0.8 
0.8 

0.8 

1.0 
1.0 
1.0 

1.0 

1.0 
1.0 

0.6 
0.6 
0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 

0.6 
0.6 
0.8 

0.6 
0~8~ 
0.8 

1.0 
1.0 

1.0 
1.25 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 
0.6 

0.6 

0.6 
0.8 
0.8 
1.0 
1.0 
1.25 

0.8 

0.8 
1.0 
1.25 
1.25 
1.5 
1.5 

1.0 
1.0 
1.25 
1.5 

1.25 
1.25 
1.5 
1.5 

0.6 
0.6 

0.6 

0.6 
0.8 
0.8 

0.6 
0.8 
1.0 

0.8 
1.0 

1.25 

1.0 
1.0 

1.25 

1.0 

1.25 

1.25 
1.5 
1.5 

0.6 
0.6 
0.6 
0.6 

0.6 
0.6 

oTJT 

0.8 
1.0 
1.25 

1.0 
1.0 

1.25 
1.5 

1.25 
1.5 

0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

0.8 
0.8 
1.0 

1.0 
1.0 

1.25 

1.25 
1.5 
1.5 

1.5 
1.5 

1.5 

1.5 

1.5 
2.0 
2.0 

2.0 
2.0 

2.0 
2.0 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

0.8 

1.25 
1.25 

1.25 
1.5 

1.5 
2.0 

2.0 
.0 

0.8 
0.8 
0.8 

0.8 
0~8~ 

1.0 

1.25 
1.25 
1.5 

1.5 
2.0 
2.0 

2.0 
2.0 

2.0 

2.0 
?  5 

60 

0.6 

0.8 
0.8 

1.0 

1.25 
1.25 

1.5 

1.5 

2.0 
2.0 

2.0 

.5 
.5 
~0~ 

2.5 

?.  5 

70 

0.6 

0.6 

0.8 

1.0 

1.0 

1.5 

1.5 

2.5 

2.5 
2.5 

3.0 

s7o~ 

3.0 
3.0 

3.0 

80 
100 
120 

0.6 

0.8 
0.8 
0.8 

0.8 

0.8 

0.8 
1.0 
1.0 

1.0 

I7o~ 

1.25 

1.25 
1.5 
1.5 

1.5 
1.5 
1.5 

1.5 

1.5 

2.0 
2.0 

2.0 

2.5 

27s~ 

2.5 

2.5 
2.5 

3.0 
3.0 
4.0 

0.8 

0.8 
0.8 

1.0 
1.0 

1.25 
1.25 

2.0 

2.5 

3.0 

.0 

3.0 

3.0 
4.0 

0.8 

1.0 

2.0 

2.0 

3.0 

3.0 

.0 

4.0 

Semi  and  Indirect  Lighting-CEiLiNG  2  4  FEET  ABOVE  WORK  PLANE 


TABLE  6      ROOM  INDEX 
For    Finding    Coefficient    of    Utilization    from    Table    5 


Direct  Lighting-sou RCES  2O  FEET  ABOVE  WORK  PLANE 


ROOM  1 
WIDTH 

ROOM    LENGTH—  FEET 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50 

60 

70 

80 

100 

120  1  140 

10 

200 

8 
10 
12 

0.8~ 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

14 
~7<r 
18 
20 
~24 
30 
35 
40 
50 
~60^ 
~70~ 
80 

Too" 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 
0.8 

0.8 

0.8 
1.0 

1.0 

1.0 
1.0 

ITcT 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

1.0 
1.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

1.0 





0.6 

0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.6 
0~8~ 

0.8 

o7i~ 

0.8 

i7o~ 

0.8 

0.8 

0.8 

T7o~ 

1.0 
1.0 

1.0 
1725 

1.0 
1.25 

1.25 
1.25 

1.25 
1.5 

0.6 

1.0 

1.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

1.5 

1.5 

0.6 

0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.8 
0.8~ 

0.8 

0.8 

1.0 

1.0 

T25 

1.25 

1.25 

1.25 

1.5 
1.5 

1.5 

1.5 
2.0 

1.5 
2.0 

1.5 
2.0 

0.6 

0.6 

1.0 

1.0 

1.0 

1.25 

1.5 

1.5 

1.5 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

1.0 

1.0 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.0 

2.5 

2.5 

0.6 
0.6 

0.6 
0.6 

0.6 

0.6 
0.8 

0.8 
0.8 

0.8 

0.8 

1.0 
1.0 

1.25 
1.25 

1.25 

1.5 

1.5 

2.0 
2.0 

2.0 
2.0 

2.0 
2.5 

2.5 
2.5 

2.5 

2.5 
3.0 

2.5 
3.0 

0.6 

0.8 

1.0 

1.5 

1.5 

1.5 

3.0 

120 

0.6 

0.6 

0.8 

0.8 

0.8 

0.8 

1.0 

1.25 

1.25 

1.5 

1.5 

2.0 

2.0 

2.5 

2.5 

3.0 

3.0 

3.0 

3.0 

Semi  and  Indirect  Lighting-CEiLiNG  3Q  FEET  ABOVE  WORK  PLANE 


Direct  Lighting- sou  RCES  24  FEET  ABOVE  WORK  PLANE 


ffE 

ROOM    LENGTH—  FEET 

*£ 

10 

12 

14 

16 

18 

20  |   24 

30 

35 

40 

50 

60 

70 

80 

100 

120 

140 

170 

200 

8 
10 

























12 
~14~ 









0.6 



0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 
0.8 

0.8 
0.8 
0.8 
1.0 
1.0 



0.6 

0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 
0.6 
0.8 

0.6 
0.6 

0.6 

0.8 

16 
~18~ 

~2<r 

).6 

0.6 

0.6 

0.8 
0.8 
0.8 
1.0 



0.6 
0.6 
0.6 

0.6 

0.6 

0.8 

0.8 
0.8 







0.6 
0.6 

0.6 

0~6~ 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.8 

24 

0.6 

0.8 

0.8 

1.0 

30 

~sT 

~40~ 

~5<r 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 
0.6 

0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.8 
0.8 

0.6 
0.8 
0.8 
0.8 
0.8 

0.8 
0.8 

0.8 
0.8 
0.8~ 

0.8 
0.8 
1.0 
1.0 

0.8 
0.8 
1.0 
1.25 

0.8 
1.0 
1.0 

1.25 

0.8 
1.0 
I?25 
1.25 

1.0 

foT 

1725 

1.0 

1.0 

1.25 
1.25 

0.6 
0.6 
0.6 

0.6 

1.25 
1.25 

1.25 
1.25 
1.5 



0.6 
0.6 

0.8 
0.8 
1.0 

1.5 
1.5 
2.0 

0.6 
0.6 

1.0 

i7o~ 

1.5 

1.5 
1.5 

60 

0.6 

0.6 

0.6 

0.6 

0.8 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

70 

0.6 

0.6 

0.6 

0.6 

0.6 

0,6 

0.8 

0.8 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

80 
100~ 
12<T 



0.6 

0.6 

0.6 

0.6 

0.6 

0.6 
0.8 
0.8 

0.8 
0.8 

0.8 
1.0 
1.0 

1.0 
1.25 

1.25 

1.5 

1.5 

1.5 
1.5 

1.5 
2.0 
2.0 

2.0 
2.0 
2.5 

2.0 
2.5 
2.5 

2.0 

2.0 
2.5 
3.0 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.6 
0.8 

1.25 

1.5 

1.5 
1.5 

2.5 
3.0 

1.0 

1.25 

1.5 

1.5 

2.0 

Semi  and  Indirect  Lighting-CEiLiNG  3  Q  FEET  ABOVE  WORK  PLANE 


TABLE  6      ROOM  INDEX 
For    Finding    Coefficient    of    Utilization    from    Table    5 


Direct  Lighting-sou RCES  3O  FEET  ABOVE  WORK  PLANE 


?H 

ROOM    LENGTH—  FEET 

*? 

10 

12 

14 

16 

13 

20 

24 

30  |    35 

40 

50 

60 

70 

80 

100  1  120 

140 

170 

200 

8 
10 
12 

14 
16 

~TiT 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

20 
~24~ 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 
0.8 
1.0 

30 
35 
40 







0.6 

0.6 
0.6 
0.6 

0.6 

0.6 

0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.6 
0.8 

0.8 
0.8 

0.8 
0.8 

0.8 
1.0 

— 





0.6 
0.6 

0.6 

0.6 

0.6 

0.6 

0.6 
0.6 

0.6 

0.8 

0.8 
0.8 

0.8 
1.0 

0.8 
1.0 

1.0 
1.0 

1.0 
1.25 

1.0 
1.25 

1.0 

1.25 

50 
~60~ 

— 



0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.8 

0.8 

1.25 

1.25 
1.5 

0.6 

0.6 

0.8 

0.8 

1.0 

1.0 

1.0 

1.25 

1.25 

1.25 

1.5 

70 
80 
10<T 



0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.8 

1.0 

1.0 

1.25 

1.25 

1.25 
1.5 

1.5 
T7T 

1.5 
1.5 

1.5 

1.5 

1.5 
2.0 

0.8 

1.0 

1.0 

1.25 

1.25 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

1.0 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

120 

0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

1.0 

1.25 

1.25 

1.5 

1.5 

1.5 

2.0 

2.0 

2.0 

2.5 

Semi  and  Indirect  Lighting-CEiLiNG  45  FEET  ABOVE  WORK  PLANE 


Direct  Lighting-sou RCES  4O  FEET  ABOVE  WORK  PLANE 


SE 

ROOM    LENGTH—  FEET 

8y 
** 

10 

12 

14 

16 

18 

20 

24 

30 

35 

40 

50   1    60 

70 

80 

100 

120 

140 

170 

|~ 

8 











— 



10 
12 
14 
16 

































— 









0.6 
0.6 

0.6 
0.6 
0.8 
0.8 

18 
20 
24 















0.6 

0.6 
0.6 







0.6 
0.6 

0.6 
0.6 

0.6 
0.6 
0.6 

0.6 
0.6 
0.6 

30 
~35~ 













0.6 
0.6 

0.6 
0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

40 





0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 
0.6 

0.6 

0.6 

0.6 

0.8 

0.8 

0.8 
1.0 

50 

0.8 

0.8 

0.8 

0.8 

0.8 

60 









0.6 

0.6 
0.6 

0.6 

0.6 

0.6 
0.6 
0.6 

0.6 

0.8 

0.8 

0.8 

1.0 

.0 

1.0 

1.0 

1.25 

1.0 

1.25 

70 

0.6 
0.6 

0.6 
0.6 

0.6 
0.8 

0.8 
0.8 

0.8 
0.8 

0.8 
1.0 

1.0 
1.0 

.0 

1.0 

80 

.25 

1.25 

1.25 

1.5 

100 









0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

1.0 

1.0 

1.0 

1.25 

.25 

1.5 
1.5 

1.5 
1.5 

1.5 

120 

0.6 

0.6 

0.6 

0.6 

0.6 

0.8 

1.0 

1.0 

1.25 

1.25 

.5 

1.5 

Semi  and  Indirect  Lighting-CEiLiNG   6O  FEET  ABOVE  WORK  PLANE 


42 


TABLE  7  LUMEN  OUTPUT  OF  MULTIPLE  MAZDA  LAMPS 

Subject  to  Change  Without  Notice 


Size  of 
Lamp 
in 
Watts 

110-115-120  Volt 
Standard  Lighting  Service 

220-230-240-250  Volt 

MAZDA  C 

MAZDA  B 

Daylight 
MAZDA 

MAZDA  C 

MAZDA  B 

Approximate  Lumen  Output,  Clear  Lamps 


IO 

80 

JC 

TO/") 

oc 

24ot 

2OO 

•*J 

AOO 

40 

450* 

coot 

4.^0 

—  ^L-  _ 

60 

620 

. 

75 

880$ 

600 

_______ 

IOO 

1300 

ooo 

I  OOO 

1050 

I  CT) 

2IOO 

1400 

2OO 

30OO 

2  IOO 

2600 

4QOO 

3/LOO 

4-200 

9OOO 

<;8oo 

7800 

5<ju 

*7CO 

I40OO 

/ov 

2OOOO 

17^00 

*  White  MAZDA. 

fThese  two  sizes  in  mill  type  construction  give  200  and  420  lumens 
respectively.  5 

$The  75-watt  white  Mazda  lamp  gives  approximately  770  lumens. 


43 


TABLE  8 

COMPUTED  ILLUMINATION  VALUES 
Using  Depreciation  Factor  of  1.3 

(See  Page  17  for  method) 


Area  in 
Square 
Ft.  per 
Lamp 

Size  of  Lamp 

COEFFICIENT  OF  UTILIZATION 

.14 

.16 

.18 

.20 

.22 

.25 

.28 

.32 

.36 

.40 

.45 

.50 

.55 

.60 

.65 

.70 

Watts 

Lumens 

FOOT  -CANDLES 

60 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

2.3 
3.8 
5.6 

8.8 

2.7 
4.3 
6.4 
10.0 

3.0 

4.8 
7.2 
11.3 

3.3 
5.4 
7.9 
12.6 

3.7 
5.9 

8.7 
13.8 

4.2 

6.7 
9.9 
15.7 

4.7 
7.5 
11.1 
17.6 

5.3 
8.6 
12.7 
20.1 

6.0 
9.7 
14.3 
22.6 

6.7 
10.8 
15.9 
25.1 

7.5 
12.1 
17.9 
28.3 

8.3 
13.5 
19.9 
31.4 

9.2 
14.8 
21.8 
34.6 

10.0 
16.2 
23.8 
37.7 

10.8 
17.5 
25.8 
40.8 

11.7 

18.8 
27.8 
44.0 

70 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

2.0 
3.2 

4.8 
7.5 

2.3 
3.7 

1:1 

2.6 
4.2 
6.1 
9.7 

2.9 
4.6 
6.8 
10.8 

3.1 
5.1 
7.5 
11.8 

3.6 
5.8 
8.5 
13.5 

4.0 
6.5 
9.5 
15.1 

4.6 
7.4 
10.9 
17.2 

5.1 
8.3 
12.3 
19.4 

5.7 
9.2 
13.6 
21.5 

6.4 
10.4 
15.3 
24.2 

7.1 
11.5 
17.0 
26.9 

7.9 
12.7 
18.7 
29.6 

8.6 
13.8 
20.4 
32.3 

9.3 
15.0 
22.1 
35.0 

10.0 
16.2 
23.8 
37.7 

80 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.8 
2.8 
4.2 
6.6 

2.0 
3  2 

2.2 
3  6 

2.5 
4  0 

2.8 
4  4 

3.1 
5  0 

3.5 

5  7 

4.0 
6  5 

4.5 

7  3 

5.0 
8  1 

5.6 
9  1 

6.2 
10  1 

6.9 
11  1 

7.5 
12  1 

8.1 
13  1 

8.7 
14.1 
20.9 
33.0 

4.8 
7.5 

5.4 

8.5 

6.0 
9.4 

6.6 
10.4 

7.4 
11.9 

8.3 
13.2 

9.5 
15.1 

10.7 
17.0 

11.9 
18.8 

13.4 
21.2 

14.9 
23.6 

16.4 
25.9 

17.9 
28.3 

19.4 
30.6 

90 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.6 
2.5 
3.7 
5.9 

1.8 
2.9 

4.2 
6.7 

2.0 
3.2 

4.8 
7.5 

2.2 
3.6 
5.3 

8.4 

2.4 
3.9 
5.8 
9.2 

2.8 
4.5 
6.6 
10.5 

3.1 
5.0 
7.4 
11.7 

3.6 
5.7 
8.5 
13.4 

4.0 
6.5 
9.5 
15.1 

4.5 
7.2 
10.6 
16.8 

5.0 
8.1 
11.9 
18.8 

5.6 
9.0 
13.2 
20.9 

6.1 
9.9 
14.5 
23.0 

6.7 
10.8 
15.9 
25.1 

7.2 
11.7 
17.2 

27.2 

7.8 
12.6 
18.5 
29.2 

100 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.4 
2.3 
3.3 
5.3 

1.6 
2.6 
3.8 
6.0 

1.8 
2.9 
4.3 
6.8 

2.0 
3.2 

4.8 
7.5 

2.2 
3.6 
5.2 
8.3 

2.5 
4.0 
5.9 
9.4 

2.8 
4.5 
6.7 
10.6 

3.2 

5.2 
7.6 
12.1 

3.6 
5.8 
8.6 
13.6 

4.0 
6.5 
9.5 
15.1 

4.5 
7.3 
10.7 
17.0 

5.0 
8.1 
11.9 

18.8 

5.5 
8.9 
13.1 
20.7 

6.0 
9.7 
14.3 

22.6 

6.5 
10.5 
15.5 
24.5 

7.0 
11.3 
16.7 
26.4 

110 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.3 
2.1 
3.0 
4.3 

1.5 
2.4 
3.5 
5.5 

1.6 
2.6 
3.9 
6.2 

1.8 
2.9 
4.3 
6.9 

2.0 
3.2 

4.8 
7.5 

2.3 
3.7 
5.4 
8.6 

2.5 
4.1 
6.1 
9.6 

2.7 
4.7 
6.9 
11.0 

3.3 
5.3 

7.8 
12.3 

3.6 

5.9 
8.7 
13.7 

4.1 
6.6 
9.8 
15.4 

4.5 
7.3 
10.8 
17.1 

5.0 
8.1 
11.9 
18.8 

5.5 
8.8 
13.0 
20.6 

5.9 
9.5 
14.0 
22.3 

6.4 
10.2 
15.2 
24.0 

120 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.2 
1.9 

2.8 
4.4 

1.3 
2.2 
3.2 
5.0 

1.5 
2.4 
3.6 
5.7 

1.7 
2.7 
4.0 
6.3 

1.8 
3.0 
4.4 
6.9 

2.1 
3.4 
5.0 
7.9 

2.3 

3.8 
5.6 
8.8 

2.7 
4.3 
6.3 
10.1 

3.0 
4.8 
7.1 
11.3 

3.3 
5.4 
7.9 
12.6 

3.8 
6.1 
8.9 
14.1 

4.2 
6.7 
9.9 
15.7 

4.6 
7.4 
11.0 
17.3 

5.0 
8.1 
12.0 
18.8 

5.4 
8.8 
13.0 
20.4 

5.8 
9.4 
14.0 
22.0 

130 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.1 
1.7 
2.6 
4.1 

~1.0 
1.6 
2.4 
3.8 

1.2 
2.0 
2.9 
4.6 

1.1 

1:? 

4.3 

1.4 
2.2 
3.3 
5.2 

1.5 
2.5 
3.7 

5.8 

1.7 
2.7 
4.0 
6.4 

1.9 
3.1 
4.5 

7.2 

2.2 
3.5 
5.1 
8.1 

2.5 
4.0 
5.9 
9.3 

2.8 
4.5 
6.6 
10.4 

3.1 
5.0 

7.4 
11.6 

3.5 
5.6 
8.3 
13.1 

3.8 
6.2 
9.2 
14.5 

4.2 
6.8 
10.1 
16.0 

4.6 
7.5 
11.0 
17.4 

5.0 
8.1 
11.9 
18.9 

5.4 
8.7 
12.8 
20.3 

140 

100 
150 
200 
300 

1300 
2100 
3100 
4900 

1.3 
2.1 
3.1 
4.9 

1.4 
2.3 
3.4 
5.4 

1.6 
2.5 
3.8 
5.9 

1.8 
2.9 
4.3 
6.7 

2.0 
3.2 

4.8 
7.5 

2.3 
3.7 
5.5 
8.6 

2.6 
4.2 
6.1 
9.7 

2.9 
4.6 
6.8 
10.8 

3.2 
5.2 

7.7 
12.1 

3.6 
5.8 
8.5 
13.5 

3.9 
6.3 
9.4 

14.8 

4.3 
6.9 
10.2 
16.2 

4.6 
7.5 
11.1 
17.5 

5.0 

8.1 
11.9 

18.8 

160 

150 
200 
300 
500 

2100 
3100 
4900 
8800 

1.4 
2.1 
3.3 
5.9 

1:1 

3.8 
6.8 

1.8 
2.7 
4.2 
7.6 

2.0 
3.0 
4.7 
8.5 

2.2 
3.3 
5.2 
9.3 

2.5 
3.7 
5.9 
10.6 

2.8 
4.2 
6.6 
11.8 

3.2 
4.8 
7.5 
13.5 

3.6 
5.4 

8.5 
15.2 

4.0 
5.9 
9.4 
16.9 

4.5 
6.7 
10.6 
19.0 

5.0 
7.4 
11.8 
21.2 

5.6 
8.2 
13.0 
23.3 

6.1 
8.9 
14.1 
25.4 

6.6 
9.7 
15.3 
27.5 

7.1 

10.5 
16.5 
29.6 

180 

150 
200 
300 
500 

2100 
3100 
4900 
8800 

1.3 

1.8 
2.9 
5.3 

1.4 
2.1 
3.4 
6.0 

1.6 
2.4 
3.8 
6.8 

1.8 
2.6 
4.2 
7.5 

2.0 
2.9 
4.6 
8.3 

3'.3 
5.2 
9.4 

2.5 
3.7 
5.9 
10.5 

2.9 
4.2 
6.7 
12.0 

3.2 
4.8 
7.5 
13.5 

3.6 
5.3 
8.4 
15.0 

4.0 
5.9 
9.4 
16.9 

4.5 
6.6 
10.5 
18.8 

4.9 
7.3 
11.5 
20.7 

5.4 
7.9 
12.6 
22.6 

5.8 
8.6 
13.6 
24.4 

6.3 
9.3 
14.7 
26.3 

200 

150 
200 
300 
500 

2100 
3100 
4900 
8800 

1.1 
1.7 
2.6 

4.7 

1.3 
1.9 
3.0 
5.4 

1.5 
2.1 
3.4 
6.1 

1.6 

2.4 
3.8 
6.8 

1.8 
2.6 
4.1 
7.4 

2.0 
3.0 
4.7 
8.5 

2.3 
3.3 
5.3 
9.5 

2.6 
3.8 
6.0 
10.8 

2.9 
4.3 
6.8 
12.2 

3.2 
4.8 
7.5 
13.5 

3.6 
5.3 
8.5 
15.2 

4.0 
6.0 
9.4 
16.9 

4.4 
6.5 
10.4 
18.6 

4.8 
7.1 
11.3 
20.3 

5.3 
7.7 
12.3 
22.0 

5.7 
8.3 
13.2 
23.7 

220 
250 

150 
200 
300 
500 

210.0 
310T) 
4900 
8800 

1:0 

1.5 
2.4 
4.3 

1.2 
1.7 

2.7 
4.9 

1.3 
1.9 
3.1 
5.5 

1.5 

2.2 
3.4 
6.2 

1.6 
2.4 
3.8 
6.8 

1.8 
2.7 
4.3 

7.7 

2.1 
3.0 

4.8 
8.6 

2.4 
3.5 
5.5 
9.8 

2.6 
3.9 
6.2 
11.1 

2.9 
4.3 
6.9 
12.3 

3.3 
4.9 
7.7 
13.8 

3.7 
5.4 
8.6 
15.4 

4.0 
5.9 
9.4 
16.9 

4.4 
6.5 
10.3 
18.5 

4.8 
7.0 
11.1 
20.0 

5.1 
7.5 
12.0 
21.5 

200 
300 
500 
750 

3100 
4900 
8800 
14000 

1.3 
2.1 
3.8 
6.0 

1.2 
1.9 
3.4 
5.4 

1.5 
2.4 
4.3 
6.9 

1.4 
2.2 
3.9 
6.2 

1.7 
2.7 
4.9 

7.8 

1.9 
3.0 
5.4 
8.6 

2.1 
3.3 
6.0 
9.5 

2.4 
3.8 
6.8 
10.8 

2.7 
4.2 
7.6 
12.1 

3.1 

4.8 
8.7 
13.8 

3.4 
5.4 
9.7 
15.5 

3.8 
6.0 
10.8 
17.2 

4.3 
6.8 
12.2 
19.4 

4.8 
7.5 
13.5 
21.5 

5.2 
8.3 
14.9 
23.7 

5.7 
9.0 
16.2 

25.8 

6.2 
9.8 
17,6 
28.0 

6.7 
10.6 
18.9 
30.2 

280 

200 
300 
500 
750 

3100 
4900 
8000 
14000 

1.5 
2.4 
4.4 
6.9 

1.7 
2.7 

4.8 
7.7 

1.9 
3.0 
5.3 

8.5 

2.1 
3.4 
6.0 
9.6 

2.4 
3.8 
6.8 
10.8 

2.7 
4.3 
7.7 
12.3 

3.1 

4.8 
8.7 
13.8 

3.4 
5.4 
9.7 
15.4 

3.8 
6.1 
10.9 
17.3 

4.3 
6.7 
12.1 
19.2 

4.7 
7.4 
13.3 
21.2 

5.1 
8.1 
14.5 
23.1 

5.5 

8.8 
15.7 
25.0 

6.0 
9.4 
16.9 
26.9 

44 


TABLE  8 

COMPUTED   ILLUMINATION  VALUES 
Using  Depreciation  Factor  of  1.3 

(See  Page  17  for  method) 


Area  In 
Square 
Ft.  per 
Lamp 

Size  of  Lamp 

COEFFICIENT  OF  UTILIZATION 

14 

.16 

.18 

.20 

.22 

.25 

.28 

.32 

.36 

.40 

.45 

.50 

.55 

.60 

.65 

.70 

Watts 

Lumens 

FOOT-CANDLES 

320 

360 

200 
300 
500 
750 

3100 
4900 
8800 
14000 

1.0 

1.6 
3.0 
4.7 

1.2 
1.9 
3.4 
5.4 

1.3 
2.1 
3.8 
6.1 

1.5 
2.4 
4.2 
6.7 

1.6 
2.6 
4.7 
7.4 

1.9 
2.9 
5.3 

8.4 

2.1 
3.3 
5.9 
9.4 

2.4 
3.8 
6.8 
0.8 

2.7 
4.2 
7.6 
2.1 

3.0 
4.7 
8.5 
3.5 

3.4 
5.3 
9.5 
5.1 

3.7 
5.9 
0.6 
6.8 

4.1 
6.5 
1.6 

8.5 

4.5 
7.1 
12.7 
20.2 

?:? 

13.8 
21.9 

5.2 

8.2 
14.8 
23.6 

200 
300 
500 
750 

3100 
4900 
8800 
14000 

0.9 
1.5 
2.6 
4.2 

1.1 

1.7 
3.0 

4.8 

1.2 
1.9 
3.4 
5.4 

1.3 
2.1 
3.8 
6.0 

1.5 
2.3 
4.1 
6.6 

1.7 
2.6 
4.7 
7.5 

1.9 
2.9 
5.3 
8.4 

2.1 
3.4 
6.0 
9.6 

2.4 
3.8 
6.8 
0.8 

2.7 
4.2 
7.5 
2.0 

3.0 

4.7 
8.5 
13.5 

3.3 
5.2 
9.4 
15.0 

3.6 
5.8 
0.3 
6.4 

4.0 
6.3 
11.3 
18.0 

4.3 
6.8 
12.2 
19.4 

4.6 
7.3 
13.2 
20.9 

400 

200 
300 
500 
750 

3100 
4900 
8800 
14000 

0.8 
1.3 
2.4 
3.8 

0.9 
1.5 
2.7 
4.3 

1.1 

1.7 
3.0 

4.8 

1.2 
1.9 
3.4 
5.4 

1.3 
2.1 
3.7 
5.9 

1.5 

2.4 
4.2 
6.7 

1.7 
2.6 
4.7 
7.5 

1.9 
3.0 
5.4 
8.6 

2.1 
3.4 
6.1 
9.7 

2.4 
3.8 
6.8 
10.8 

2.7 
4.2 
7.6 
12.1 

3.0 
4.7 
8.5 
13.5 

3.3 

5.2 
9.3 

4.8 

3.6 
5.7 
10.2 
16.2 

3.9 
6.1 
11.0 
17.5 

4.2 
6.6 
11.8 
18.8 

450 

200 
300 
500 
750 

3100 
4900 
8800 
14000 

0.7 
1.2 
2.1 
3.4 

0.8 
1.3 
2.4 

3.8 

1.0 
1.5 

2.7 
4.3 

1.1 
1.7 
3.0 

4.8 

1.2 
1.8 
3.3 
5.3 

1.3 
2.1 
3.8 
6.0 

1.5 
2.3 
4.2 
6.7 

1.7 

2.7 

4.8 

7.7 

1.9 
3.0 
5.4 
8.6 

2.1 
3.4 
6.0 
9.6 

2.4 

3.8 
6.8 
10.8 

2.6 
4.2 
7.5 
12.0 

2.9 
4.6 
8.3 
13.2 

3.2 
5.0 
9.0 
14.4 

3.5 
5.4 
9.8 
15.6 

3.7 
5.9 
10.5 
16.8 

500 

300 
500 

M 

4900 
8800 
14000 
20000 

1.1 
1.9 
3.0 
4.3 

1  r 

2.  '2 
3.4 
4.9 

1.4 
2.4 
3.9 
5.5 

1.5 

2.7 
4.3 
6.2 

1.7 
3.0 

4.7 
6.8 

1.9 
3.4 
5.4 

7.7 

2.1 
3.8 
6.0 
8.6 

2.4 
4.3 
6.9 

9.8 

2.7 
4.9 
7.8 
1.1 

3.0 
5.4 
8.6 
12.3 

3.4 
6.1 
9.7 
13.8 

3.8 
6.8 
10.9 
15.4 

4.1 
7.4 
11.9 
16.9 

4.5 
8.1 
12.9 
18.4 

4.9 
8.8 
14.0 
20.0 

5.3 

9.5 
15.1 
21.5 

600 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.9 
1.6 
2.5 
3.6 

1.0 
1.8 
2.9 
4.1 

1.1 
2.0 
3.2 
4.6 

1.3 
2.3 
3.6 
5.1 

1.4 
2.5 
4.0 
5.6 

1.6 
2.8 
4.5 
6.4 

1.8 
3.2 
5.0 

7.2 

2.0 

3.6 
5.7 

8.2 

2.3 
4.1 

6.5 
9.2 

2.5 
4.5 
7.2 
10.3 

2.8 
5.1 
8.1 
11.5 

3.1 
5.6 
9.0 
12.8 

3.5 
6.2 
9.9 
14.1 

3.8 
6.8 
10.8 
15.4 

4.1 
7.3 
11.7 
16.7 

4.4 
7.9 
12.6 
18.0 

3.8 
6.8 
10.8 
15.4 

700 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.8 
1.4 
2.2 
3.1 

0.9 
1.5 
2.5 
3.5 

l.( 

2.  '8 
4.0 

1.1 
1.9 
3.1 
4.4 

1.2 
2.1 
3.4 

4.8 

2  'A 

3.8 
5.5 

1.5 

2.7 
4.3 
6.2 

1.7 
3.1 
4.9 
7.0 

1.9 
3.5 
5.5 
7.9 

2.2 
3.9 
6.2 

8.8 

2.4 

4.4 
6.9 
9.9 

2.7 
4.8 
7.7 
11.0 

2.0 
5.3 
8.5 
12.1 

3.2 

5.8 
9.2 
13.2 

3.5 
6.3 
10.0 
14.3 

800 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.7 
1.2 
1.9 
2.7 

0.8 
1.4 
2.2 
3.1 

0.8 
1.5 
2.4 
3.5 

0.9 
1.7 

2.7 
3.8 

1.0 
1.9 

S3 

1.2 
2.1 
3.4 

4.8 

1.3 
2.4 
3.8 
5.4 

1.5 
2.7 
4.3 
6.2 

1.7 
3.0 

4.8 
6.9 

1.9 
3.4 

5.4 

7.7 

2.1 

3.8 
6.1 

8.7 

2.4 
4.2 
6.7 
9.6 

2.6 
4.7 
7.4 
10.6 

2.8 
5.1 
8.1 
11.5 

3.1 
5.5 
8.8 
12.5 

3.3 
5.9 
9.4 
13.5 

900 

300 
500 
700 
1000 

4900 
8800 
14000 
20000 

0.6 
1.1 

1.7 
2.4 

0.7 
1.2 
1.9 
2.7 

0.8 
1.4 
2.2 
3.1 

0.8 
1.5 
2.4 
3.4 

0.9 
1.7 
2.6 
3.8 

1.0 
1.9 
3.0 
4.3 

1.2 
2.1 
3.4 
4.8 

1.3 
2.4 
3.8 
5.5 

1.5 
2.7 
4.3 
6.2 

1.7 
3.0 

4.8 
6.8 

1.9 
3.4 
5.4 

7.7 

2.1 
3.8 
6.0 
8.6 

2.3 
4.1 
6.6 
9.4 

2.5 
4.5 
7.2 
10.3 

2.7 
4.9 
7.8 
11.1 

2.9 
5.3 
8.4 
12.0 

1000 

300 
500 
700 
1000 

4900 
8800 
14000 
20000 

0.5 
0.9 
1.5 
2.2 

0.4 
0.8 
1.3 

1.8 

0.4 
0.7 
1. 

0.3 
0.6 
0.9 
1.3 

0.6 
1.1 
1.7 
2.5 

0.7 
1.2 
1.9 

2.8 

0.8 
1.4 
2.2 
3.1 

0.8 
1.5 
2.4 
3.4 

0.9 
1.7 

2.7 
3.8 

1.1 
1.9 
3.0 
4.3 

1.2 
2.2 
3.4 
4.9 

1.4 
2.4 
3.9 

1.5 

2.7 
4.3 

1.7 
3.0 

4.8 

1.9 
3.4 
5.4 

2.1 
3.7 
5.9 

2.3 
4.1 
6.5 
9.2 

2.4 
4.4 
7.0 
10.0 

2.6 
4.7 
7.5 
10.8 

1200 
1400 
1600 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.5 
0.9 
1.4 
2.1 

0.6 
1.0 
1.6 
2.3 

0.6 
1.1 

1.8 
2.6 

0.7 
1.2 
2.0 

2.8 

0.8 
1.4 
2.2 
3.2 

0.7 
1.2 
1.9 
2.7 

0.9 
1.6 
2.5 
3.6 

1.0 
1.8 
2.9 
4.1 

0.9 
1.5 
2.5 
3.5 

1.1 
2.0 
3.2 
4.6 

1.3 
2.3 
3.6 
5.1 

1.4 
2.5 
4.0 
5.8 

1.6 
2.8 
4.5 
6.4 

1.7 
3.1 
4.9 
7.1 

1.9 
3.4 
5.4 

7.7 

2.0 
3.7 
5.8 
8.3 

2.2 
3.9 
6.3 
9.0 

1.9 
3.4 
5.4 

7.7 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.4 
0.8 
1.2 

1.8 

0.5 
0.9 
1.4 
2.0 

0.5 
1.1 

2.1 

"(U) 
0.8 
1  3 

0.6 
1.1 
1.7 
2.4 

0.8 
1.4 
2.2 
3.1 

0.7 
1.2 
1  9 

1.0 
1.7 

2.8 
4.0 

1.1 
1.9 
3.1 
4.4 

1.2 
2.2 
3.5 
4.9 

1.3 
2.4 
3.8 
5.5 

1.5 
2.7 
4.2 
6.0 

1.3 
2.3 
3  7 

1.6 
2.9 
4.6 
6.6 

1.4 

2.5 
4.0 

5.8 

1.8 
3.1 
5.0 
7.1 

1.5 

2.8 
4.4 
6.2 

2.2 

3.5 
5.0 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.4 
0.7 
1  1 

0.4 
0.8 
1  2 

0.5 
0.9 
1  5 

0.6 
1.1 
1  7 

0.8 
1.4 
2  2 

0.8 
1.5 
2  4 

0.9 
1.7 
2  7 

1.1 
1.9 
3  0 

1.2 
2.1 
3  4 

1.6 
3.0 

4.7 
6.7 

1.3 

2.4 
3.8 
5.4 

1.1 
1.9 
3.0 
4.3 

1.5 

1.7 

1.9 

2.1 

2.4 

2.7 

3.1 

3.5 

3.8 

4.3 

0.8 
1.5 
2.4 
3.5 

4.8 

0.9 
1.7 
2.7 
3.8 

5.3 

2000 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.3 
O.S 
0.8 
1. 

0.3 
0.5 
0.9 
1.2 

0. 
0. 
0. 
1. 

0.3 
0.6 
1.0 
1.4 

0. 
0. 
0. 
1. 

0.4 
0. 
1. 

0.4 
0.7 
1.2 
1.7 

0.5 
0.8 
1.3 
1.9 

0.5 
0.9 
1.5 

2.2 

0.4 
O.S 
1.2 
1.7 

0.6 
1. 
1.7 
2.5 

0.7 
1.2 
1.9 

2.8 

0.5 
1.0 
1.6 
2.2 

0.8 
1.4 
2.2 
3.1 

0.6 
1.1 
1.7 

2.5 

1.0 
1.9 
3.0 

4.2 

2'.( 
3.2 
4.6 

2500 

300 
500 
750 
1000 

4900 
8800 
14000 
20000 

0.2 
0. 
0. 
0. 

0. 
0. 
0. 
1. 

0.3 
0.6 
O.S 
1.4 

0.4 
0.7 
1. 
1.. 

0.5 
0.9 
1.4 

2.0 

0.7 
1.2 
1.9 

2.8 

O.i 

2!: 
3.1 

0.8 
1.5 
2.4 
3.4 

0.9 
1.6 
2.6 
3.7 

1.0 
1.8 
2.8 
4.0 

45 


PART  III 
STORE  AND  SHOW  WINDOW  LIGHTING 

To  illuminate  a  store  successfully,  light  must  be  provided 
where  it  is  needed.  Granting  first  that  the  light  is,  therefore, 
upon  the  objects  or  surfaces  to  be  seen,  and  not  in  the  eyes,  there 
yet  remains  the  requirement  that  it  must  be  not  only  sufficient 
in  amount  for  the  particular  store  under  consideration  but  must 
be  of  the  proper  diffusion,  color,  and  direction.  Obviously  the  il- 
lumination adequate  for  one  store  might  be  insufficient  for  an- 
other, and  conversely  the  quality  or  amount  necessary  for  one 
type  of  establishment — for  example  a  Jewelry  store — might  be 
extravagant  in  another,  such  as  a  Music  or  Furniture  store.  In 
the  latter  case  a  soft,  well-diffused  illumination  is  all-important 
since  the  best  of  wood  and  upholstery  suffers  under  a  glary  light. 
The  Jewelry  store,  however,  involves  entirely  different  treat- 
ment. A  direct  undiffused  component  of  light  assists  in  giving 
the  jewels  and  cut  glass  a  sparkling  appearance.  Shadowless  il- 
lumination would  make  the  faceted  gems  appear  flat  and  would 
detract  much  from  the  display,  and  furthermore;  the  soft,  mel- 
low light  that  would  enrich  the  appearance  of  a  pearl,  would 
give  no  life  whatever  to  the  diamond. 

GENERAL  CLASSES  OF  STORE  LIGHTING 

Each  store  presents  an  individual  problem,  but  for  conven- 
ience of  discussion,  retail  stores  may  be  divided  into  three  classes 
according  to  quality  and  direction  of  the  lighting  required : 

First:  Those  whose  unchanging  floor  or  counter  op- 

erations require  a  particular  location  of  the  light  sources. 
Second:  Those  for  which  general  illumination  with  the 
most  convenient  symmetrical  placing  of  the  outlets  is 
satisfactory. 

Third:  Those  stores  in  which  artistic  and  decorative 

appearance  is  the  chief  consideration. 

The  first  class  includes  stores  of  the  following  types :  Jewelry, 
Haberdashery,  Cigar,  Shoe,  Drygoods,  Hardware,  Drug,  and 
Stationery.  In  these  the  lighting  system  must  be  designed  to  il- 
luminate the  particular  sections  where  merchandise  is  inspected, 
usually  the  counters  on  wihich  goods  are  displayed  and  sold. 
The  majority  of  stores  in  this  class  have  two  rows  of  counters, 
one  on  each  side  and  extending  the  length  of  the  store.  This 
would,  of  course,  suggest  a  double  row  of  lighting  units.  A 
common  error,  however,  is  to  place  a  single  row  down  the  center 
aisle  with  the  inevitable  result  that  the  customer  casts  a  shadow 


on  the  exact  spot  where  light  is  most  needed,  and  that  the  light 
is  too  strong  where  the  customer  is  walking,  and  too  weak  where 
he  is  looking. 

The  Shoe  store  is  a  representative  type  of  this  first  general 
class.  Here  light  is  required  primarily  on  the  floor  where  the 
shoe  is  tried  on,  secondarily  upon  the  side  walls  where  the  clerk 
should  instantaneously  read  box  labels.  Most  Shoe  stores  have 
two  rows  of  chairs  back  to  back  down  the  center  of  the  store  and 
it  is  therefore  wfell  to  have  two  rows  of  units  located  over  the 
front  edge  of  the  chairs  so  that  neither  the  salesman  nor  the  cus- 
tomer casts  a  shadow  on  the  shoe. 

The  second  class,  those  requiring  general  uniform  illumination 
from  the  most  economical  and  symmetrical  spacing  of  the  out- 
lets, includes  Clothing,  Fur,  Carpet,  Furniture,  Butcher,  Baker, 
and  Grocery  stores.  A  single  row  of  units  in  the  long  narrow 
room  is  generally  satisfactory,  although  local  illumination  plays 
a  rather  important  part  in  some  cases.  Carpet  stores  require 
special  lighting  where  vertical  rug  racks  are  used.  In  Clothing 
stores  additional  lights  are  often  needed  in  front  of  wall  cases  or 
mirrors. 

The  third  class  covers  Confectionery,  Florist,  and  Music 
stores,  and  exclusive  shops  w^hich  lend  themselves  to  what  might 
be  termed  "ultra-artistic  treatment."  Here  individual  taste,  of 
course,  plays  an  all-important  part,  but  the  chief  thought  should 
be  first  to  provide  a  background  or  a  foundation  illumination  of 
soft,  not  too  bright,  and  well-diffused  character,  using  either  di- 
rect or  indirect  fixtures  selected  for  their  ornamental  fitness. 
Lighting  from  concealed  sources  is  often  most  pleasing  for 
stores  of  this  character.  Then,  to  the  soft  broadcast  illumination 
may  be  added  highlights  or  colored  spots,  such  as  from  wall 
brackets  or  portable  table  lamps  with  tinted  shades,  avoiding  ut- 
terly all  bare,  glittering,  or  garish  light  sources. 

THE  VALUE  OR  AMOUNT  OlF  ILLUMINATION 
REQUIRED 

With  these  general  principles  in  mind,  the  next  consideration 
is  the  amount  of  light  required  for  various  kinds  of  stores.  The 
tendency  today  is  toward  illumination  that,  while  not 
lavish,  is  yet  not  limited  by  the  old  requisites  of  carbon 
filament  or  oil  lamp  days,  but  which  reaches  the  higher  value? 
needed  for  sure  and  easy  vision.  It  is  therefore  wise  to  install  a 

47      ', 


system  which,  in  its  adequacy  and  its  flexibility,  will  not  be  ob- 
solete in  a  few  years.  Five  foot-candles  of  illumination  should 
be  the  minimum  value  for  any  good  retailing  store,  while  eight 
is  an  average  of  general  practice  in  metropolitan  districts.  Many 
stores,  however,  find  twelve  and  fifteen  foot-candles  desirable, 
and  do  not  consider  this  excessive  in  comparison  to  daylight 
which  reaches  several  hundred. 

The  following  table  gives  the  recommended  standards  of  il- 
lumination that  experience  has  found  satisfactory  in  store  light- 
ing: 

TABLE   No.   1 

VALUES  OF  ILLUMINATION  RECOMMENDED  FOR 
RETAIL  STORES 

Type  of  Foot-Candles 

Store  Range 

Art    5-10 

Baker    4-8 

Book 4  -    8 

Butcher    4-    8 

Carpet    5  -  10 

Rug  Rack  10-20 

China     4-    8 

Cigar    S-io 

Clothing    5-IO 

Confectionery 5-10 

Decorator 5  -  10 

Department  (See  each  department) 

Drugs    5-io 

Dry  Goods   5  -  10 

Florist 4-    8 

Furniture 4  -    8 

Furrier 5  -  10 

Grocery   4-    8 

Haberdashery    . .  5  -  10 

Hardware   4  -    8 

Hat    5-io 

Jewelry    5  -  10 

Leather    4-    8 

Millinery   5  -  10 

Music    4-    8 

Notions    4-    8 

Piano    4  -    8 

Shoes . . S-io 

Stationery 4-    8 

Note : — The  foot-candle  is  the  unit  of  illumination  value  or  "in- 
tensity" of  light  upon  a  surface.  The  foot-candles  of  illumina- 
tion may  be  thought  of  as  similar  to  the  feet  of  thickness  of  a 
snowfall.  Foot-candles  must  not  be  confused  with  candle  power, 
the  unit  of  light  brilliancy  or  intensity  of  radiation ;  nor  with 
lumens,  the  units  of  light  quantity. 


It  has  been  necessary  to  give  a  ran^c  instead  of  a  specific 
value  for  each  type  of  store,  as  its  location  and  the  kind  of  mer- 
chandise sold  determine  the  illumination  required.  To  permii 
the  customer  to  examine  dark-colored  merchandise  as  readily  as 
that  of  a  lighter  shade,  the  higher  value  must  be  provided.  An- 
other consideration  is  the  character  of  the  neighboring  stores. 
One  merchant  cannot  afford  to  struggle  along  on  the  minimum 
value  suitable  for  the  mere  discernment  of  objects,  if  his  neigh- 
bors, in  addition  thereto,  have  so  brightly  lighted  or  so  taste- 
fully decorated  their  stores  that  their  cheerful  and  welcome  at- 
mosphere makes  the  former  establishment  appear  dark  and  un- 
inviting by  contrast. 

Glare  should  not  be  mistaken  for  Illumination.  Stores 
equipped  with  shallow  open  reflectors,  and  especially  those  using 
bare  lamps,  generally  do  not  have  as  much  actual  useful  illumi- 
nation as  those  in  which  well-diffused  or  shielded  light  sources 
permit  comfortable  and  accurate  vision.  The  glare  from  the 
brilliant  illuminants  only  blinds  the  customer  and  thus  the  in- 
stallation  defeats  its  purpose. 

LIGHTING  UNITS,  OR  LUMINAIRES 

In  order  to  direct  the  maximum  amount  of  light  where  it  will 
be  of  service  and  to  shield  or  soften  the  brilliant  light  sources 
in  the  range  of  vision,  reflecting  and  diffusing  equipment  must 
be  used. 

Stores  may  be  satisfactorily  illuminated  by  luminaires  of 
anyone  of  the  three  classes  into  which  reflecting  equipment  is  di- 
vided, direct,  including  the  enclosing  and  semi-enclosing  globes ; 
semi-indirect,  sending  more  light  upward  than  downward ;  totally 
indirect,  sending  all  the  light  upward.  This  classification  de- 
pends upon  whether  the  majority  of  light  rays  are  transmitted 
directly  to  the  plane  of  work  or  whether  they  are  largely  or 
toally  re-directed  from  the  ceilings  and  walls. 

Open  bottom  reflectors  are  usually  the  most  economical 
equipment,  but  their  appearance  can  hardly  be  compared  to  some 
of  the  other  types.  With  them  there  is  also  the  objection  of 
possible  glare  and  specular  reflections  and  it  is  therefore  advisa- 
ble to  use  lamps  having  the  lower  portion  of  the  bulb  of  diffus- 
ing glass ;  i.e.,  diffusing  bulb  or  bowl  enameled.  On  the  other 
hand  some  direct  rays  of  light  are  necessary  in  jeWelry  store  il- 
lumination and  open  prismatic  reflectors  of  an  ornamental  style 

49 


Fig.  No.  1 — Typical  Store  Lighting  Luminaire* 


A      S.mi    l,,,li,.-.l     H,,wl 
It      l.,.l,,,-,l     Howl 


(       (.,-.,.-!    Idiwl 
I)     !>„,,  I    K,.||..,  l.u 


i:       I-'.,,,  l,,r.i,,K      <.l.,l,,- 

I       liowl    .iii.l    Upper    I'L.i. 


Fig.  No.  1A — Typical  Store  Lighting  Luminairet 

G-Indirect   Bowl  H-Globe  and   Cover  1-PrUm.tic   Reflector 

J-Enclosinf  Globe  K-Seml- Indirect  Bowl  L-Bowl  *nd  Reflector 

ti 


Fig.  No.   IB — Typical  Store  Lighting  Luminaires 

M— Bowl   and   Reflector  N— Semi-Indirect,   Enclosing 

O— Enclosing,    Light    Directing  P— Semi- Indirect 

using  for  example,  pendant  crystal  prisms  around  the  reflector, 
will  be  found  both  attractive  and  appropriate  equipment  for 
lighting  jewels  and  cut  glass. 

The  various  semi-indirect  and  totally  indirect  luminaires  are 
used  where  light-colored  walls  and  ceilings  permit,  and  when  a 
soft,  well-diffused  light  is  desired. 

TIhe  most  popular  luminaires  for  store  lighting  are  the  en- 
closing diffusing  globes,  the  present  style  for  reasons  of  effici- 
ency as  well  as  decoration  being  those  of  the  squat  shape.  These 
globes  are  nearly  dust-tight  and  thus  require  only  a  relatively 
small  maintenance,  besides  being  capable  of  softening  the  dis- 
comforting brilliancy  of  the  bare  gas-filled  Mazda  lamps  with 
consequent  light  absorption  losses  of  not  more  than  20  per  cent. 

52 


Table  2 
Lamps  Recommended  for  Store  Use 


Luminaire 

MAZDA  LAMP 

Wattage 

Type 

Finish 

Open  Reflectors 

25,  40,  50 

50 
100,  150,  200 

75 

Mazda  B 

White  Mazda  (C) 
Mazda  C 
Mazda  C 

Clear  or   Diffusing 
Bulb 

Bowl  Enameled 
Diffusing  Bulb 

Enclosing  Globes, 
Semi-Enclosing, 
Semi-Indirect,  or 
Totally  Indirect 

75,  100,  150  I 
200,  300,  500  $ 
150,  200,  300,  500 

Mazda  C 
Daylight  Mazda 

Clear  Bulb 
Clear  Bulb 

Window  Reflectors 

75,  100,  150 
100,  150 

Mazda  C 
Daylight  Mazda 

Clear  Bulb 
Clear  Bulb 

Floor  and 
Table  Lamps 

40,  50 
50 

Mazda  B 
White  Mazda  (C) 

Diffusing  Bulb 

Show  Cases 

25,40 
15,25 
15 

Mazda  B 
(Tubular  Bulb) 
Mazda  B 
(Round  Bulb) 
Mazda  B 
(Candelabra) 

Clear  Bulb 
Clear  Bulb 

Clear  or  Diffusing 
Bulb 

Wall  Brackets 
With  Shade 

Without  Shade 

25,  40,  50,  60 
75 
15 

25 

25,  40,  50 
50 

Mazda  B 
Mazda  C 
Mazda  B 
(Flame-Candelabra) 
Mazda  B 
(Round  Bulb) 
Mazda  B 
White  Mazda  '(C) 

Clear  Bulb 
Clear  Bulb 
Diffusing  Bulb 

Diffusing  Bulb 
Diffusing  Bulb 

Candelabra  and 
Decorative  Types 

25,40 

50 
25,  40,  50 

Mazda  B 
(Round  Bulb) 
White  Mazda  (C) 
Mazda  B 

Diffusing  Bulb 
Diffusing  Bulb 

Entrance  Enclosing 
Globes  and  Hemi- 
spheres 

75,  100 

Mazda  C 

Clear  Bulb 

53 


ENTRANCE  DOORWAY  LIGHTS 

A  well-lighted  store  requires  a  brightly  illuminated  entrance, 
particularly  on  a  brightly  lighted  street.  Tihe  air  of  welcome 
and  activity  is  most  necessary,  and  the  passer-by  who  sees  a 
window  display  should  sub-consciously  find  the  entrance 
clearly  defined  and  attractive.  Some  merchants  find  it  profit- 
able to  light  the  side  walk  in  front  of  their  store  or  at  least  to 
use  an  electric  sign  which  can  thus  serve  a  double  purpose. 

An  enclosing  globe  of  the  ceiling  type  or  a  close  fitted  ceiling 
hemisphere  is  recommended  for  entrance  lighting.  For  the  ma- 
jority of  small  stores  a  75  or  loo-watt  Mazda  C  lamp  will  be 
sufficient  for  this  purpose.  Here,  above  all  else,  the  luminaire 
should  be  dust  and  insect  proof,  and  when  the  window's  are 
washed  this  entrance  light  should  also  be  cleaned. 


NIGHT  LIGHTS 

As  a  protection  against  robbery  after  closing  hours  a  lamp 
well  placed  and  burning  all  night  will  illuminate  the  store  suf- 
ficiently to  allow  the  policeman  or  watchman  to  see  the  whole 
of  the  interior.  This  lamp  is  usually  placed  where  it  will  bring 
into  prominence  the  safe,  vault,  rear  entrance,  or  specially  valu- 
able stocks.  As  a  rule  a  5O-watt  Mazda  B  lamp  or  a  75 -watt 
Mazda  C  lamp  is  used. 

An  attractive  means  of  supplementing  the  display  window 
area  and  providing  night  illumination,  is  to  keep  a  wall  case  in 
the  rear  of  the  store  lighted  throughout  the  night.  In  addition 
to  displaying  merchandise  an  illuminated  wall  case  will  sil- 
houette clearly  the  figure  of  anyone  moving  about  in  the  store. 

The  cost  of  burning  the  5O-watt  lamp  would  not  exceed 
seven  cents  per  night. 

COLOR  MATCHING  AND  COLOR  QUALITY 

The  accurate  identification  of  color  is  often  necessary  in 
merchandising.  Clothing  and  Carpet  stores,  Haberdashery 
shops,  and  ladies  apparel  rooms  especially,  should  be  equipped 
with  some  means  of  reproducing  daylight  illumination.  Mazda 
Daylight  lamps  will  provide  a  means  of  approximating  day- 
light quality,  as  will  some  enclosing  cased-glass  globes,  one 

54 


layer  of  which  is  blue  glass  absorbing  some  of  the  red  and 
yellow  rays  emanating  from  the  regular  Mazda  C  lamp. 

An  effective  means  of  displaying  rugs  is  to  install  a  dual 
lighting  system,  one  circuit  consisting  of  Mazda  daylight  and  the 
other  of  clear  bulb  Mazda  lamps.  It  is  thus  possible  to  show 
the  rug  as  it  appears  under  both  daylight  and  artificial  illu- 
mination. Merchants  selling  rugs  under  these  conditions  have 
less  returned  goods,  and  will  find  many  dyes  wihose  tones  are 
visibly  enriched  by  light  of  a  carefully  chosen  color  quality. 

The  Mazda  Daylight  lamp  can  be  used  very  appropriately 
over  mirrors  in  Clothing  stores  where  suits  and  dresses  are 
tried  on.  Flower,  Fur,  Hat,  and  even  Jewelry  stores  can  use 
them  in  connection  with  clear  lamps  to  bring  out  blue  colors 
in  better  relation  to  the  reds  and  yellows. 

For  very  accurate  color  matching  and  identification,  there 
are  available  specially  designed  units  employing  standard  clear 
bulb  Mazda  C  lamps,  the  light  from  which  is  filtered  through 
a  specially  designed  blue  glass  screen.  One  type  of  color  matching 
unit  is  for  counter  use  in  the  lighting  of  small  merchandise,  such 
as  silks,  ribbons,  and  neckties.  There  are  also  pendant  types 
for  suspending  in  front  of  mirrors  in  the  examination  of  wearing 
apparel  in  clothing  stores.  Such  color  quality  of  illumination 
is  unrivaled  for  displays  of  cravats,  ribbons,  colored  buttons, 
spool  silk  and  cotton,  trimmings,  and  flowers. 

SHOW   CASE  LIGHTING 

Show  cases,  both  the  counter  and  wall  type,  are  another 
means  at  the  disposal  of  the  merchant  for  displaying  his  goods. 
They  are  really  miniature  show  windows  and  as  such  should 
be  properly  illuminated,  else  their  heavy  investment  cost  and 
their  valuable  space  is  not  100  per  cent,  capitalized. 

Show  cases  are  for  showing  and  not  storing  merchandise.  Tf 
sufficiently  illuminated,  careful  inspection  may  be  made  without 
moving  and  handling  the  various  articles. 

There  are  two  types  of  reflecting  equipment  preferable  for 
show  case  lighting;  first,  the  individual  mirrored  glass  reflectors, 
and,  second,  the  metal  trough  reflectors  extending  the  length 
of  the  case.  The  illuminated  show  case  shown  in  Fig.  No.  2 
illustrates  how  inconspicuously  these  latter  units  can  be  in- 
stalled in  an  all-glass  case.  The  exception  to  the  usual  practice 
of  concealing  the  units  as  much  as  possible  is  in  the  lighting 

55 


of  candy  displays,  wax  ornaments,  etc.,  where  tne  merchandise 
is  affected  by  the  heat  of  the  lamps.  An  attractive  method  of 
solving  this  problem  is  to  use  small  ornamental  lamps  on  top 
of  the  case  and  thus  provide  the  illumination  from  outside. 
The  chief  consideration  is  to  furnish  more  illumination  in  these 
cases  than  is  supplied  for  the  store  itself  in  order  that  they  will 


Fig.  2 


stand  out  by  contrast;  approximately   15  to  25  foot-candles  is 
usually  the  minimum   value. 

For  the  lighting  of  show  cases,  25-watt  Mazda  lamps  on  18 
to  24-inch  centers  will  be  sufficient.  Attention  is  called  to  the 
tubular  lamps  available,  and  to  the  small  decorative  types 
whose  use,  clear  or  colored,  should  be  better  known  and  more 
extensive. 

56 


Plan  A 
SHOE  STORE— THE  INSTALLATION  AND  THE  PLAN 


Interior  Illumination 

Area  of  Store  (48  x  25) 1200  Sq.  Ft. 


Illumination  Desired  (Table  i) 

Utilization  Factor 

Depreciation  Factor   (20%) 
Number  of  Outlets 


9  Ft.-Candles 
.36 
.80 
8 


Lumens  Required  per  Outlet  = 


1200x9 


=     4690 


. 36  x. Sox  8 
Use  3OO-watt  Mazda  C  Lamps 
Wattage  per  Square  Foot  of  Floor  =  2 
Show  Window  Illumination 

loo-watt  Mazda  C  lamps  on  i6-inch  Centers. 
Wattage  per  Square  Foot  of  Window  Floor  =  15 


57 


Plan  B 

GROCERY  STORE— THE  INSTALLATION  AND  THE 

PLAN 


v<200W 


n 


Interior  Illumination 

Area  of  Store   (40  x  12^) 500  Sq.  Ft. 

Illumination   Desired       (Table    i) 6  Ft. -Candles 

Utilization    Factor    32 

Depreciation   Factor    (20%) 80 

Number  of   Outlets 4 

500  x  6 

Lumens  Required  Per  Outlet  = =r    2930 

•32x  .80  x  4 

Use  2oo-watt  Mazda  C  Lamps. 
Wattage  per  Square  Foot  of  Floor  —  1.6 

Show  Window  Illumination 

Two  roc-watt  Mazda  C  Lamps. 

Wattage  per  Square  Foot  of  Window  Floor  =  10. 

58 


SHOW  WINDOW  LIGHTING 

Merchants  endeavor  to  locate  their  stores  not  only  on  busiest 
streets  but  on  the  busier  side  of  the  street.  The  more  people 
that  see  the  merchandise,  the  more  the  sales.  Consequently 
in  order  to  realize  more  fully  upon  the  large  investment  in 
window  space,  it  is  essential  to  light  up  the  windows  as  soon 
as  dusk  falls  or  perhaps  even  during  the  daylight,  and  to  keep 
them  working  at  100  per  cent,  efficiency  even  after  the  store 
is  closed,  as  long  as  pedestrians  are  abroad.  This  can  be  ac- 
complished by  a  key  switch  on  the  outside  of  the  store,  to  be 
operated  by  a  watchman  or,  in  a  more  satisfactory  way,  by  an 
automatic  time-switch. 

There  should  be  enough  light  so  that  the  wlindows  are  not 
dim  by  comparison  with  those  adjacent.  The  lighting  must 
be  designed  to  conceal  the  light  sources  from  the  vision  of  the 
spectators  and  in  addition  to  so  shield  and  place  them  that  there 
is  no  direct  reflection  from  the  polished  wood  or  glass  back- 
ground of  the  window.  The  usual  and  an  excellent  method  of 
concealing  the  lamps  and  reflectors  is  by  a  cloth  or  a  painted 
glass  valance.  The  prismatic  glass  reflectors  are  best  suited 
for  illuminating  these  transparent  advertising  valances.  In  case 
of  deep  windows  with  a  long  side  bordering  the  entrance,  or 
of  open-back  show  windows,  it  is  of  equal  importance  to  con- 
ceal the  units  from  the  back  as  well  as  the  front  by  hanging 
behind  them  a  second  cloth  valance. 

In  another  style  of  window  lighting  equipment  the  lamps 
sre  mounted  horizontally  in  shallow!  metal  troughs  lined  with 
mirrored  glass.  These  can  be  very  inconspicuously  installed 
either  at  the  top  or  bottom  of  the  window  and  are  easily  con- 
cealed from  the  rear  by  having  the  trough  deep,  and  the  metal 
match  the  interior  trim.  Metal  partitions  fitted  across  the 
trough  prevent  a  direct  view  of  bare  lamps  when  the  observer 
is  standing  at  the  side  of  the  window. 

The  care  that  is  given  to  window  lighting  approaches  that 
of  the  theatrical  stage.  Spot  lights  are  used  to  accentuate  parti- 
cular features.  Footlights  of  approximately  one  quarter  the 
strength  of  the  overhead  lights  are  used  to  soften  the  shadows. 
For  general  use  a  system  of  alternate  clear  and  Mazda  daylight 
lamps  is  recommended.  This  will  provide  light  close  enough 
to  daylight  quality  and  yet  warm  enough  for  correct  color  im- 

59 


pressions  of  most  merchandise.  Windows  trimmers  are  now 
employing  colored  light  to  produce  the  more  studied  artistic 
effects  and  to  show  merchandise  to  its  best  advantage,  as  de- 
scribed in  the  next  section. 

The  appearance  of  a  show  window  arid  the  attractiveness 
of  the  display  may  be  enhanced  by  the  use  of  side  wall  brackets 
and  stand  lamps.  Relatively  small  wattage  lamps  will  be  ample, 
as  such  equipment  should  not  be  counted  upon  to  illuminate 
the  window  but  merely  to  serve  as  an  added  attraction. 

The  safe  practice  in  lighting  show  windows  is  to  use  the 
equipment  designed  especially  for  that  particular  service.  There 
is,  however,  an  exception  found  in  some  small  stores  such  as 
Grocery,  Bakery,  and  Butcher  shops.  Here  the  windows  do  not 
usually  have  backgrounds,  and  displays  of  merchandise  are  not 
given  as  much  decorative  consideration  as  in  other  types  of 
stores.  But  non-glaring  light  is  needed  and  can  be  excellently 
provided  by  locating  the  outlets  as  shown  in  Plan  B  for  the 
Grocery  store.  Three  or  four  open  deep-bowl  glass  reflectors 
mounted  at  the  top  of  the  window  about  12  inches  from  the 
glass  will  illuminate  the  window,  supplement  the  interior  light-, 
ing  and  will  not  be  objectionable  from,  the  standpoint  of  glare. 

SHOW  WINDOW  EQUIPMENT 

The  principal  types  of  window  lighting  reflectors  are  shown 
in  Fig.  No.  4.  In  addition  to  these  there  is  the  trough  re- 
flecting equipment  previously  metioned.  Both  the  mirrored  and 
prismatic  units  can  be  obtained  in  various  styles  suitable,  as 
occasion  demands,  for  high,  deep,  or  shallow  windows.  In  some 
instances  adjustable  holders  are  provided  permitting  the  use 
of  one  reflector  for  various  types  of  windows. 

For  color  effects  the  mirrored  glass  unit,  Fig.  No.  4 
(B)  is  available  With  the  detachable  gelatin  color  screen  shown. 
The  prismatic  reflector  (A)  is  also  furnished  with  screens  of 
similar  material  that  can  be  attached  by  clips  to  the  bottom 
of  the  unit.  The  reflector  (C)  uses  a  glass  color  cap  that  fits 
over  the  lamp,  while  the  trough  reflector  can  be  had  with  screens 
of  natural  colored  glass,  or  gelatin. 

All  of  these  color-producing  devices  are  easily  attached  or 
changed.  Combinations  of  the  three  primary  colors,  red,  green, 
and  yellow,  ordinarily  supplied  will  be  sufficient  for  most  needs 

60 


although  with  gelatin  screens  or  lamp  color  dips,  there  becomes 
available  a  large  variety  of  colors. 


^ 


ABC 

Fig.   No.  4. — Show  Window   Reflectors 

SHOW  WINDOW  ILLUMINATION  CALCULATIONS 

The  planning  of  the  lighting  for  windows,  excepting  the 
artistry  and  the  color  harmonies,  need  not  involve  the  calcu- 
lations required  in  designing  the  general  interior  illumination. 
The  majority  of  show  windows  are  practically  of  a  standard 
lype  and  with  the  specially  designed  equipment  the  illumina- 
tion may  be  determined  simply  by  the  proper  spacing  of  the 
units.  The  general  practice  is  to  use  loo-watt  Mazda  C  lamps 
spaced  18  inches  apart.  Outside  of  metropolitan  centers,  or 
on  dimly  lighted  streets,  this  spacing  may  be  increased  up  to  a 
maximum  of  24  inches.  For  lower  illumination  a  75-watt  lamp 
would  be  used.  The  tendency,  however,  is  towlard  higher  valuer 
and  in  metropolitan  districts  loo-watt  lamps  with  12-inch  spac- 
ing is  considered  good  practice.  In  Plan  A,  page  57,  loo-watt 
iamps  are  spaced  on  about  i6-inch  centers. 

As  previously  explained,  in  the  open-back  windows  of 
Grocery,  Bakery,  and  similar  stores,  the  standard  window  equip- 
ment should  not  be  used  unless  a  drop  curtain  or  shield  is  hung 
behind  them.  Here  again  the  calculations  involved  in  the  gen- 
eral interior  lighting  are  not  necessary.  A  simple  method  of 
planning  the  lighting  on  a  watt-per-square-foot  basis  is  very 
convenient  and  will  usually  be  found  satisfactory.  This  pro- 
cedure may  also  be  followed  and  will  serve  as  a  check  in  win- 
dows, using  equipment  as  shown  in  Fig.  No.  4. 

61 


Using  3  to  5  watts  per  square  foot  will  produce  a  moderately 
high  illumination,  while  10  watts  per  square  foot  is  a  good 
average  figure  for  lighting  show  windows.  The  present  practice, 
however,  in  metropolitan  centers,  is  to  use  20  watts  per  square 
foot,  unless  spot  lights  are  employed  to  supplement  the  over- 
head units. 

On  this  basis  in  Plan  B,  page  58,  we  will  assume  10  watts 
per  square  foot.  The  floor  area  of  each  window  is  20  square 
feet,  which  multiplied  by  10  gives  200  watts  per  window.  This 
is  provided  by  2  units  of  100  watts  each. 


WIRING  AND  CONTROL 

The  lighting  switches  should  be  conveniently  located  and 
the  wiring  system  so  laid  out  that  flexible  and  easy  control  is 
provided.  This  applies  particularly  to  Furniture,  Rug,  and 
similar  stores  where  certain  sections  are  lighted  only  when  a 
customer  is  inspecting  merchandise.  Switches  should  be  lo- 
cated near  the  entrance  to  a  room  or  department.  In  case  of 
more  than  one  entrance,  three-way  switches  permitting  control 
at  two  points  will  be  found  convenient. 

In  the  wiring  of  show  windows  two  circuits  controlling  alter- 
nate units  are  frequently  advisable.  This  will  permit  the  use 
of  part  of  the  equipment  during  the  late  afternoon  when  the 
artificial  illumination  supplements  the  failing  daylight,  or  will 
facilitate  the  alternation  of  colors  if  flashers  be  connected  to  one 
or  more  circuits. 

It  is  important  to  provide  an  ample  number  of  convenience 
outlets,  i.e.,  wall  or  baseboard  receptacles,  column  outlets,  etc., 
throughout  the  store.  These  will  eliminate  dangling  wires  and 
permit  easy  connections  for  fans,  vacuum  cleaners,  portable  and 
stand  lamps,  decorative  festoons,  department  signs,  and  elec- 
trical display  devices.  Show  windows  should  also  be  equipped 
with  auxiliary  outlets  for  fans,  electrical  displays,  etc.,  and 
particularly  with  one  or  more  receptacles  at  the  front  edge  or 
corner  of  the  window,  top  and  bottom,  for  spot  lights. 

The  foresighted  merchant  must  remember  that  the  planning 
cf  the  lighting,  and  the  part  that  light  is  to  play  in  benefiting 
his  sales,  begins  with  the  work  of  the  electrical  contractor,  and 
with  the  placing  of  the  outlets. 

62 


PART   IV 
INDUSTRIAL   LIGHTING 

Requirements  of  Good  Industrial  Illumination 

The  requirements  which  must  be  met  in  the  choice  of  re- 
flecting equipment  and  in  the  design  of  a  satisfactory  lighting 
installation  for  industrial  plants  are : 

1.  A  steady  light  of  sufficient  intensity  on  all  working- 
surfaces  whether  in  horizontal,  vertical,  or  oblique  planes; 

2.  A  comparable  intensity  of  light  on  adjacent  areas  and 
on  the  walls ; 

3.  Light  of  a  color  and  spectral  character  suited  to  the 
purpose  for  which  is  is  employed; 

4.  Freedom   from  glare  and  from   glaring  reflections ; 

5.  Light  so  directed  and  diffused  as  to  avoid  objection- 
able shadows  or  contrasts  of  intensity; 

6.  A   system    which    is    simple,    reliable,    easy    of    main- 
tenance, and  reasonable  in  initial  and  operating  cost. 

Complete  satisfaction  cannot  be  expected  from  an  installa- 
tion in  which  any  one  of  these  requirements  has  been  neglected. 
Thousands  of  manufacturers  have  taken  advantage  of  the  abund- 
ance of  light  obtained  from  the  high-power  Mazda  C  lamps  to 
duplicate  daylight  conditions  in  their  plants,  but  others,  either 
through  carelessness  or  ignorance,  have  given  no  thought  to 
the  choice  of  proper  reflecting  equipment  and  installation. 
Naturally,  such  practice  is  not  only  wasteful  of  light,  but  the 
glare  from  the  unshielded  lamp  filaments  detracts  in  large 
measure  from  the  effectiveness  of  the  system  and,  in  fact,  may 
prove  to  be  a  positive  menace  to  the  safety  and  eyesight  of 
the  employees. 
Light  on  the  Work 

Today,  work  of  many  kinds,  including  the  most  intricate 
operations  and  those  requiring  the  utmost  precision,  must  be 
carried  on  throughout  the  twenty-four  hours.  If  artificial  light 
•:ould  be  had  for  the  asking,  no  plant  would  be  content  with  a 
lower  standard  of  illumination  by  ni^ht  than  by  day.  Table  i 
summarizes  the  minimum  values  of  daylight  that  operators  in 
typical  factor:es  consider  sufficient. 

Each  figure  p-iven  is  the  mean  of  a  number  of  observations 
and  the  measurements  extended  over  both  clear  and  cloudy 
days.  The  aim  was  to  secure  data  which  represented  good  aver- 

63 


Table  No.  i 
Intensities   of   Daylight   Illumination   in   Foot-Candles 

Values    obtaining    when    daylight    was    deemed    just    sufficient    for    processes    carried    on. 


Factory  Product 

Grade  of  Work 
Fint             Medium            Rough 

Engine  lathes                   venE£Tff£M.x 

10 
6  —  15 

7 
2  —  15 

3 

0-5   —  9 

Automatic  engine  lathes 

1  4 
2   —  30 

1  2 
2  —  30 

1  0 
1   —   15 

Machine  forgings 

6 
2   —  15 

5 

1    —   10 

Special  machinery 

1  0 
4  —   20 

7 
3   —   15 

Lamps 

10 
5-16 

9 

11   —   15 

Vacuum  cleaners 

17 
7   —  25 

1  1 
3   —   20 

Automobiles 

5 
2  —  11 

5 

2-8 

5 
3   —   11 

Automobiles  * 

1  0 
6  —   12 

3 
1   —   3 

5 
4  —  5 

Storage  batteries 

5 

1—6 

3 
0-5  —  5 

Machine  tools  and  patterns 

6 
2   —  16 

9 
3  —  35 

Sheet  iron  equipment 

1  0 
1   —  20 

5 

1    —   12 

8 
2   —    15 

Machine  gears 

7 
3-16 

8 
5   —  18 

5 

1-15 

Hardware 

1  0 
1—20 

1  0 
1   —  20 

4 
0-5   —   12 

Printing  machinery 

5 

1   —  15 

3 

0-5   —  5 

Sewing  machines 

4 
1   —   8 

2 

Cloth  bags 

5 
3   —   10 

7 
3   —   10 

Clothing 

1  0 
10—20 

4 
7   —   15 

Furniture 

5 

3  —  20 

5 

0-5   —   12 

Average 

1  0 
4  —  18 

7 
3   —    1  5* 

1  -5  -   10 

*Saw  tooth  roof. 

age  working  conditions ;  and  factory  processes  were  divided 
roughly  into  three  groups  in  accordance  with  the  relative  nec- 
essity for  accurate  vision.  It  will  be  noted  that  in  general  the 
operations  requiring  closest  attention  were  ordinarily  best 
lighted,  for  wherever  possible  such  machines  are  located  near 
the  windows.  Just  below  the  data  on  horizontal  illumination 
there  are  given  in  each  case  the  results  of  readings  taken  in  two 
vertical  planes,  toward  and  away  from  the  windows. 

Obviously,  the  minimum  intensity  of  either  daylight  or  arti- 
ficial light  to  be  supplied  is  that  which  w*ill  permit  comfortable 
vision,  conserve  eyesight,  and  eliminate  accident  hazard.  Many 
states,  through  their  Industrial  Commissions,  are  beginning  to 
require  the  employer  to  make  such  minimum  provision.  In  the 
States  Codes,  intensities  for  various  classes  of  operations  are  spe- 
cified, depending  on  the  nature  and  fineness  of  the  detail  to  be 

64 


observed,  the  closeness  of  application  required,  and  the  reflection 
factor  of  the  working  surfaces.  These  intensities  are  designed  to 
protect  the  operative  who  must  work  for  long  hours  under  these 
conditions  day  after  day. 

However,  these  governmental  requirements  are  not  such  as  to 
?ssure  the  most  economical  production,  a  factor  of  vital  interest 
to  the  manufacturer,  and  to  obtain  which  considerably  higher  in- 
tensity values  are  found  necessary.  It  is  difficult  to  recommend 
the  exact  intensity  required  in  a  given  plant  from  the  economic 


Fig.  i — Successful  Application  of  Properly  Directed  and  Diffused  General 

Lighting  to    Interiors   of   this    Nature   is    Gradually 

Eliminating  the  Drop  Cord  System 

standpoint.  This  figure  necessarily  depends  upon  numerous 
factors  such  as  the  cost  of  producing  light,  the  number  and  wages 
of  the  employees,  and  the  value  of  their  output,  all  of  which  vary 
widely  in  different  establishments. 

For  good  vision,  the  color  and  fineness  of  the  materials 
worked  upon  are  important  considerations  in  determining  the 
amount  of  light  which  should  be  supplied.  An  object  is  seen  by 
the  light  which  it  reflects  rather  than  by  the  light  falling  on  it; 
hence  textile  mills  manufacturing  dark  colored  fabrics  require 
higher  intensities  than  those  mills  which  produce  light  colored 


goods.  Manufacturing  processes  involving  fine  machine  work 
c-r  fine  assembling  require  more  light  than  industries  where  a 
comparatively  low  degree  of  accuracy  suffices.  The  greater 
alertness  and  better  morale  of  the  workmen  in  brightly  lighted 
surroundings  are  at  once  apparent  in  the  greater  production  of 
the  plant. 


WML  PfiNGE  OF  DAYLIGHT 
INTENSITIES  INOOOftS-4t»SO 

WTIFICIAL  INTENSITIES  FOR 
Extra,  fine  Work 8to 60 


fine  Work 


4tolZ 


Medium  Work     3t*9 

Rough  Work         2U6 

Passageways.  Etc.. 
Indoors. 

Outdoor  Work 


FOOT-CflNDLE  INTENSITY 

10          20          JO  40  50 


10 


20 


JO 


CO 


Fig.   2 — Artificial  Lighting  Intensities   Compared  with   Interior  Daylight 

Values 

There  is  a  growing  conviction  that  no  one  should  be  called 
upon  to  work  continuously  at  any  occupation  under  an  intensity 
of  less  than  one  foot-candle  regardless  of  how  rough  the  opera- 
tion may  be.  Table  4,  of  Part  II,  Illumination  Design  Data,  lists 
the  present  standards  of  intensity  for  different  classes  of  work. 
There  is  no  doubt  that  the  use  of  higher  values  than  are  there 
listed  will  prove  profitable  in  many  cases.  It  is  a  notable  fact 
that  in  those  factories  in  which  the  most  study  has  been  devoted 
to  lighting,  the  highest  intensities  have  been  adopted,  based  upon 
ihe  experience  that  each  increase  has  led  to  still  more  economical 
production. 

Tests  by  Wm.  A.  Durgin  in  four  Chicago  plants  where  accu- 
rate cost  and  production  records  could  be  kept,  showed  that  with 
illumination  of  the  order  of  10  to  12  foot-candles,  the  production 
increased  from  10  to  35  per  cent  at  a  cost  for  lighting  of  only 


'Electrical    World,    March    1,    1919. 


Electrical    Review,    March    22,    1919. 

66 


i  to  5.5  per  cent  of  the  pay  roll.  These  shops  were  engaged  in 
various  metal  machining  and  assembling  operations  and  the  pre- 
\ious  lighting  systems  were,  in  one  case,  individual  lamps  on 
drop  cords,  and  in  the  other  three  instances,  general  lighting  sys- 
tems in  which  the  illumination  ranged  from  2  to  4  foot-candles. 

In  a  consideration  of  the  amount  of  light  necessary  for  fac- 
tory illumination,  the  criterion  must  be  the  intensity  on  all  work- 
ing surfaces,  whether  in  horizontal,  vertical,  or  oblique  planes. 
At  one  time,  consideration  was  largely  confined  to  light  on  the 
horizontal ;  yet  most  factory  work  involves  the  perception  of  ob- 
jects in  their  three  dimensions,  and  the  illumination  of  all  sur- 
faces is  important. 

Except  in  especially  unfavorable  locations,  such  as  near  the 
dark  side  wall  of  a  room,  any  of  the  systems  of  lighting  usually 
employed  can  be  expected  to  provide  an  intensity  of  illumination 
on  any  vertical  plane  equal  to  about  one-half  of  that  measured  in 
a  horizontal  plane  at  the  same  point.  This  fact  should  be  kept  in 
mind  particularly  in  designing  a  lighting  system  to  comply  with 
the  State  Codes,  which  usually  specify  only  the  value  to  be  pro- 
vided on  the  principal  plane  of  the  work,  which  may  be  vertical, 
horizontal,  or  oblique. 

The  intensity  values  used  in  industrial  lighting  as  compared 
with  the  usual  range  of  daylight  intensities  existing  in  factory 
interiors  are  shown  graphically  in  Fig.  2. 

Illumination  of  Surrounding  Surfaces 

Moderate  intensities  of  illumination  in  aisles  and  other  spaces 
intermediate  between  the  working  surfaces,  on  the  walls,  etc.,  are 
necessary  to  safety,  good  vision,  and  a  stimulating  atmosphere. 
Light  side  walls  are  conducive  to  a  cheerful  impression  of  bright- 
ness throughout  the  room.  Sources  which  direct  considerable 
light  to  the  vertical  planes,  and  light  wall  colors,  aid  materially 
in  accomplishing  this. 

The  eyes  of  the  workman  looking  up  from  his  well  illumi- 
nated machine  or  bench  are  not  adapted  for  vision  at  low  inten- 
sities ;  hence,  if  adjacent  objects  and  aisles  are  only  dimly  lighted, 
he  will  be  compelled  either  to  grope  about,  losing  time  and  risk- 
ing accident,  or  to  wait  until  his  eyes  have  become  adapted  to  the 
low  intensity.  Glancing  back  at  his  work,  he  again  loses  time 
while  the  pupils  of  his  eyes  adjust  themselves  to  the  increased 
amount  of  light  which  reaches  them.  If  long  continued,  this 

67 


condition  leads  to  fatigue,  as  well  as  to  interference  with  vision, 
and  to  accidents.  The  general  illumination  of  all  intermediate 
and  surrounding  areas  should  be  sufficient  to  allow  no  marked 
contrast  with  the  brightness  of  the  working  surfaces. 

It  is  considerations  such  as  these  that  have  led  to  the  almost 
universal  adoption  of  the  general  or  overhead  system  of  lighting 
in  modern  industrial  plants ;  they  also  constitute  strong  argu- 
ments for  the  use  of  reflecting  equipments  which  direct  a  part 
of  the  light  toward  the  side  walls  and  ceiling. 

Color  Quality  of  Light 

As  daylight  intensities  represent  the  standards  which  are  to 
be  sought  in  the  artificial  lighting  of  industrial  plants,  so  does  the 
color  of  daylight  constitute  the  standard  which  should  be  ap- 
proached in  artificial  illumination.  Through  centuries  of  use  the 
human  eye  has  adapted  itself  to  function  best  under  a  color  of 
light  found  within  the  range  over  which  natural  light  varies,  and 
light  within  this  range  will  also  be  found  most  pleasing  and  stim- 
ulating. 

Color  discrimination  forms  one  of  the  most  important  aids  to 
vision.  It  defines  outlines  and  edges  and  serves  to  identify  ob- 
jects which  may  be  similar  in  other  respects,  such  as  form,  tex- 
ture, and  reflection  factor.  The  ideal  illuminant  therefore  emits 
rays  of  all  colors.  While  the  exact  proportions  are  not  the  same, 
still,  all  of  the  colors  in  daylight  are  contained  in  the  light  emitted 
by  MAZDA  C  lamps,  and  objects  retain  their  natural  appearance 
when  viewed  under  this  light.  The  MAZDA  daylight  lamp  with 
its  specially  selected  blue-green  glass  bulb  gives  a  light  which 
is  a  further  step  toward  daylight  color  and  extremely  valuable  in 
the  manufacturing  processes  requiring  closer  color  identification 
cr  better  revelation  of  detail  through  color  contrasts.  For  dye 
making  and  color  matching,  where  extreme  accuracy  is  required, 
several  equipments  w'ith  special  absorbing  screens  are  available 
which  duplicate  the  standard  north-sky  light  with  exactness. 

Under  certain  conditions,  on  the  other  hand,  as  in  a  foundry, 
the  criterion  for  the  choice  of  an  illuminant  is  the  penetrating 
power  of  the  light.  The  appearance  of  the  sun  through  smoke, 
haze,  or  fog  evidences  the  fact  that  the  shorter  wave  lengths,  or 
'he  rays  near  the  blue  end  of  the  spectrum,  are  absorbed  or  dis- 
persed while  the  longer  wrave  lengths  pass  through.  Hence, 
under  such  conditions,  light  in  which  red  and  yellow  rays  pre- 
68 


dominate  is  the  most  effective,  and  a  clear-bulb  MAZDA  C  lamp 
will  give  better  service  than  a  MAZDA  daylight  lamp. 

Glare 

Glare  has  been  characterized  as  light  out  of  place.  It  has  been 
more  fully  denned  as  brightness  within  the  field  of  vision  of  such 
a  character  as  to  cause  discomfort,  annoyance,  interference  with 
vision,  or  eye  fatigue.  Either  definition  establishes  the  fact  that 
glare  is  undesirable. 


Fig.  3 — An  Installation  of  Mirrored-Glass  Reflectors  in  a  Foundry 

The  degree  to  which  glare  is  experienced  depends  upon  six 
principal  factors : 

i — Total  candlepower  emitted  by  the  source  in 
the  direction  of  the  eye ; 

2 — Distance  from  the  source  to  the  eye; 

3 — Intrinsic  brilliancy  of  the  source; 

4 — Contrast  in  brightness  between  the  light 
source  and  the  working  surfaces  and  surroundings; 

5 — Proximity  of  the  light  source  to  the  line  of 
vision  ; 

6 — Length  of  time  during  which  the  source  of 
glare  is  present  within  the  field  of  vision. 

69 


It  is  a  matter  of  common  experience  that  of  two  sources  of 
equal  candlepower,  that  wihich  has  the  greater  intrinsic  brilliancy 
or  candlepower  per  square  inch  is  the  source  of  greater  discom- 
fort. Too  frequently,  however,  the  consideration  of  glare  is  as- 
sumed to  be  entirely  a  question  of  intrinsic  brilliancy.  Of 
greater  importance  than  this  is  the  question  of  total  light  flux 
entering  the  eye.  A  lo-inch  opal  globe  equipped  with  a  5OO-watt 
MAZDA  C  lamp  hung  approximately  10  feet  above  the  floor  and 
10  feet  from  the  observer,  will  prove  fully  as  glaring  as  a  bare 
^5-watt  MAZDA  C  lamp  in  the  same  location.  Although  the  in- 
trinsic brilliancy  of  the  opal  globe  unit  is  only  two  or  three  times 
that  of  a  candle,  its  total  candlepower — hence  the  quantity  of 
light  which  reaches  the  eye  at  this  close  range — is  so  excessive 
that  its  effect  is  just  as  bad  as  that  of  the  filament  of  the  lower 
candlepower  MAZDA  C  lamp  which  has  an  intrinsic  brilliancy  400 
times  as  great  as  that  of  the  globe.  On  the  other  hand,  the 
same  500-watt  unit  at  twice  the  mounting  height  might  be  en- 
tirely unobjectionable  because  of  the  greatly  reduced  quantity 
of  light  which  would  then  reach  the  eye. 

Contrast  also  is  an  important  factor  in  causing  glare.  An  un- 
shielded MAZDA  lamp  hung  over  a  bench  near  a  window  causes 
no  glare  when  viewed  against  the  background  of  sky  by  day,  yet 
the  same  source  contrasting  sharply  in  brightness  with  its  back- 
ground at  night  will  be  the  cause  of  extreme  discomfort,  accen- 
tuated by  reason  of  the  fact  that  it  is  close  to  the  line  of  vision. 
The  afternoon  sun  has  only  a  fraction  of  its  noonday  brightness ; 
nevertheless,  on  account  of  its  proximity  to  the  horizon,  it  is 
much  more  likely  to  be  glaring. 

Some  sources  which  are  not  immediately  recognized  as  glar- 
ing may  cause  fatigue  when  within  the  field  of  vision  for  a  con- 
siderable period  of  time.  The  effect  of  looking  out  of  a  window 
for  a  moment  is  usually  not  at  all  unpleasant.  But  working  all 
day  at  a  desk  facing  the  same  window  would  be  decidedly  tiring. 
Specular  Reflection 

Wherever  highly  polished  surfaces  are  present,  the  reflected 
images  of  a  light  source  as  seen  in  these  surfaces  are  more  likely 
to  be  a  cause  of  discomfort  than  the  lighting  units  themselves. 
Glare  caused  by  specular  reflection  from  working  surfaces  is  par- 
ticularly trying-  because  of  the  necessity  of  directing  the  eyes 
toward  those  surfaces,  and  further,  because  the  eyes  are  by  na- 

70 


lure  especially  sensitive  to  light  rays  entering  from  below.  In 
choosing  lighting  equipment,  it  must  be  borne  in  mind  that,  al- 
though a  given  reflector  may  afford  adequate  protection  against 
direct  glare  from  the  lamp  filament,  it  will  not  protect  against 
glaring  reflections  unless  the  lamp  is  shielded  in  such  a  manner 
that  the  filament  cannot  be  seen  when  the  unit  is  viewed  from 
directly  beneath.  In  many  industrial  operations  including  the 
inspection  of  finished  surfaces,  a  moderate  degree  of  specular  re- 
flection or  sheen  will  be  found  essential. 


Fig.   4 — Freedom   from   Drop    Cords   is   Essential  where   Motors   are 
Moving    Along    in    Progressive    Assembly 

Shadows 

Differences  in  brightness  of  surfaces,  that  is,  light  and 
shadow,  are  essential  in  observing  objects  in  their  three  dimen- 
sions. Without  such  differences,  except  as  variations  in  color 
are  present,  no  outlines,  edges,  or  contours  would  be  defined;  one 
could  not  tell  whether  an  object  were  rectangular  or  circular  in 
cross  section,  whether  the  faces  were  flat,  convex,  or  concave. 
On  the  other  hand,  in  the  factory  it  is  usually  necessary  to  work 
on  surfaces  in  many  planes ;  hence,  while  dense,  sharp  shadows 
would  define  edges  and  outlines  most  distinctly,  they  might  also 
be  so  dark  as  to  interfere  with  work  in  the  shaded  areas. 

From  successful  trials  of  indirect  lighting  in  offices,  some  fac- 
tory managers  have  drawn  the  conclusion  that  the  indirect  sys- 


tern  is  ideal  for  all  locations,  and  that  it  is  simply  the  matter  of 
operating  cost  and  maintenance  which  has  prevented  the  univers- 
al application  of  this  system.  However,  the  distinction  must  be 
recognized  that  in  offices  close  scrutiny  is  limited  to  plane  sur- 
faces and  that  printed  words  and  figures  are  rendered  legible  by 
differences  in  color  and  contrasts  in  brightness  with  the  back- 
ground, and  here  specular  reflection  and  shadows  are  of  no  aid 
to  vision,  but  usually  do  harm. 

For  satisfactory  general  illumination  in  industrial  plants, 
there  must  be  no  shadows  so  dense  as  to  make  vision  difficult 
where  the  direct  light  from  one  or  two  sources  is  cut  off,  nor  so 
sharply  defined  as  to  cause  confusion  between  a  machine  part 
and  its  shadow.  In  general,  lighting  should  be  so  designed  that 
shadows  are  present,  but  they  should  be  soft  and  luminous. 

*****       * 

For  a  guide  to  the  selection  of  lighting  equipment  and  for  the 
method  to  be  followed  in  making  illumination  calculations,  the 
reader  is  referred  to  Part  II,  Illumination  Design  Data. 


Operations   of    fine   detail    may   be   well   lighted   by   an   overhead   system. 

Here  the  average  of  10  Foot-candles  is  provided  by  10'  x  10'  spacing  of 

150  and  200  Watt  Mazda  C  Lamps  in  RLM  Reflectors 


Table  2 — Good  Lighting  for  Factories 


Good  Lighting  requires  three  things: 

1.  Light  of  Suitable  Quality. 

2.  Light  of  the  Proper  Direction. 

3.  Light  in  the  Correct  Amount. 


Good  Lighting 


Suitable  Quality 


r  Absence  of  Glare. 

j  Absence  of  Reflected  Glare. 

[  Proper  Color. 


T^.       ,.       (  Shadows  Soft  and  Luminous. 
Proper  Direction  {  Uniform  Distribution. 

[Lighting  for  Safety. 

Correct  Amount    \  Lighting  for  Economical  Production. 
I  Proper  Cleaning  of  Units. 


Table  3 — Bad  Lighting  for  Factories 


Cause 

Effect 

Remedy 

Bare  Lamps. 

Glare,      eye      strain, 

The  modern  efficient 

wasted  light,  harsh 

type     of     reflector 

shadows. 

such    as    RLM 

Standard    dome. 

Miscellaneous      local 

Glare,      eye      strain, 

General  overhead  sys- 

lights  dangling  on 

danger  of  accident, 

tem. 

drop  cords. 

particularly     about 

belting  and  moving 

machinery,       short 

circuits,  breakage. 

General         System- 

"Spotty"        lighting  ; 

Proper    relation    be 

Units  too  far  apart 

areas      between 

tween        mounting 

or  too  low. 

lamps  receive  very 

height  of  un'ts  and 

little    light;    shad- 

spacing distance. 

ows  are  very  black. 

Clear    lamps    where 

Reflected    glare,    eye 

Bow  1-E  n  a  m  e  1  e  d 

polished      surfaces 

strain. 

MAZDA     C     lamps, 

are  present  on  ma- 

or    equipment     to 

terial  or  machinery. 

• 

diffuse     downward 

light  from  filament. 

Too    little    illumina- 

Time  lost   by   work- 

Larger lamps  in  suit- 

tion. 

man,      particularly 

a  b  1  e      reflectors 

on  detail  work  ;  eye 

spaced    closer    to- 

strain ;      accidents  ; 

gether  if  necessary. 

no  incentive  to  keep 

place  cleaned  up. 

Sharp,  black  shadows. 

Accidents;  time  lost; 

RLM  Standard  dome 

eye  strain. 

reflectors     properly 

spaced.    Bowl- 

enameled      MAZDA. 

C  lamps. 

Gloomy  and  cheerless 

Unpleasant    contrast 

Liberal  use  of  white 

appearance          o  f 

b  e  t  we  e  n        light 

paint    accompanied 

room. 

sources   and  back- 

in   some    cases 

ground  ;    dispirited 

where    location    is 

workmen. 

suitable  by  use  of 

glass  reflectors. 

Dusty,     dirty,     or 

Loss  of  40%  to  60% 

Institute     a     regular 

broken  equipment. 

of  the  light  paid  for. 

cleaning  schedule. 

73 


LOCATION    OF  OUTLETS  IN  TYPICAL  FACTORY 
INTERIORS 

The  following  illustrations  show  how  direct  lighting  units 
may  be  advantageously  located  according  to  bays  in  the  usual 
industrial  interior.  The  reader  is  referred  to  Page  79  for  a  dis- 
cussion of  bench  lighting. 

Design  No.  Ja.  Bays  J2  x  16  ftl       Design  No.   Jc.  Bays  J£  x  16  ftl 

Ceiling    Height— Not     Less    than    9    ft.        Ceiling    Height— Not    Less    than    Jg    ft. 
(See    also    Design    11).) 

-L  r.  f. 


Ja     '1     a     I1  I 

-t             II                     "        ( 

*3'^^6L^                 *                                            Ii          )        Wall  A  -^ 

II            i             I1 
i            il   \ 

D          D          U4       Q     |]     Q          D     ||    D( 

"1                        II        \ 

l|                         jl    \ 

L    D       j        D               V 

<o                               il 

II 
D        3        a-*-     D    n    Q       n        n 

o  j  Di!  rjTi"/ 

__L  i  JJ 

___!L__J  L_  ,_H 

ii  / 

a     II     a  n|     a     ,!     a     T 

a.       a        a       a    "    a       a        / 
n                JX 

1           ll           >| 
1            i                       I 

n             / 

11           / 
a        a       a       a    n    n     / 
/ 

n           ll           'i 
a     ll     a     L    a     [ 

'  "1  ~  ~  I1  r—  -f-- 
n     |f                                   ''   / 

ii       «*** 

a     ,|     DT|     a      ,     a     |iy 

^—  ^_    K  .    _^—&^ 

n    .?  i     n     y 

«—•=](—          U               JL            X 

SPECIFICATIONS 

1  —  •  —  -^3J  —  •  -3!~^-*^3E~^^ 
SPECIFICATIONS 

Location  —  4    Units   per   Bay   as   Shown    (48        Location  —  2  and  1  Units  per  Bay  as  Shown 
Sq.    Ft.   per    Outlet).                                                     (128    Sq.  Ft.   per  Outlet). 

Mounting    Height—  Good   Practice,    8  #    ft.        Mounting    Height—  Good    Practice,    11    ft. 
above       Floor;       Preferably,       somewhat               above    Floor.                          , 

Higher. 

Design  No.   Jd.                 Bays  J2  ^  16  ft' 
Design  No.   p.                Bays  ft  x  IQ  ft.                       Height-Not    Less    than    14    ft. 
Ceiling    Height  —  Not     Less    than    9    ft. 

(See    also    Design    ja.) 

II                      |        l|                                || 

II                               1'                                " 

Wall  A-»                                 /*' 

'-*'  3.      j,   |l                I    l^-j!                               I1               u_6' 

••-  6  '—  *p  n-  /£  '  —  »|              ||                              || 

a        a  Ii       a  4-  a  Fa         a  il       a 
ll         J                    II 
il          "°     r                Ii 

a              a  -  -  n       a       N 

1                                Ii 

a        B|       a1    |i  D         a         a 

ii             i              !  J 
1          •  "             J,/ 

i             1             j 

i     {  j    ^y 

T            T              r 
l                              ii 

a        a        a        a        a  |       a 

I, 

n               1 
1              n               i 

n       |       a-i-          a/ 

a        a  'i       a       i  a         n  '        3 

^/ 

H                                                ll 

II                    II     y^ 

ii              LX 

SPECIFICATIONS 

Location — 4  and  2  Units  per  Bay  as  Shown 

(64    Sq.    Ft.    per    Outlet). 
Mounting    Height— Good    Practice,    8J4    ft. 


SPECIFICATIONS 

Location — 1   Unit  per  Bay  as   Shown    (192 
Sq.    Ft.   per   Outlet). 


above      Floor; 
Higher. 


Preferably,      somewhat        Mounting    Height— Good    Practice,     14    ft. 


above  Floor. 


74 


Design  No.  £a.  Bays  12  x  20  ft< 

Ceiling    Height—  Not    Less    than    JQ    ft. 


Design  No.  £a.  Bays  lg  x  lg  ft. 

Ceiling    Height—  Not    Less    than    9    ft. 


6       a  !|      a  4-  ji  a  a  l|  a 

b  II  'I'  K 

1 1|  '' 

a       ail     Q-MID  all  a 


ail     D     I,  a      all     a 


a      a  'a     il  a      Dll     a 


SPECIFICATIONS 

Location — 4  and  2  Units  per  Bay  as  Shown 

(80    Sq.    Ft.    per    Outlet.) 
Mounting    Height— Good    Practice,    10    ft. 

above      Floor.       Preferably,       somewhat 

Higher. 


•/*'n4-  

D 

a-      '~T1  r 

Tjpi 

ii 

D     l|      D 

P 

D  i! 

<0|, 

1 

h 

D 

D±!l     D 

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IT" 
0      ||      D 

L).  

a    n    a 

a    1 

i 

i 

D 

o   ji   a 

a   ,|    a 

D      I 

=  ^= 

—  -I—  _ 

i"z!b"-™ 

^J 

SPECIFICATIONS 

Location— 4    Units   per    Bay   as   Shown    (64 

Sq.    Ft.    per   Outlet). 
Mounting    Height— Good    Practice,    8^    ft. 

above      Floor;      Preferably,      somewhat 

Higher. 


Design  No.  2&-  Bays  12  x  20  ftl 

Ceiling    Height— Not    Less    than     12    ft 


Design  No.  3b.  Bays  lg  x  lg  ft. 

Ceiling    Height— Not    Less    than    ]_]_    ft. 

Where  interior  is  not  likely  to  be  subdivided 
into  smaller  rooms,  4,  2  and  1  units 
per  bay  may  be  used  in  the  same  man- 
ner as  in  Design  6b.  There  will  then 
be  one  outlet  per  114  sq.  ft.  of  floor 
area. 


=-=_-^-_^  J-  =-^r  ^=  =  J    =  •=.-=.*•». 

— . ~T<  ^~-~, 


SPECIFICATIONS 

Location — 2  Units  per  Bay  as  Shown    (120 

Sq.    Ft.   per   Outlet). 
Mounting    Height— Good    Practice,    11    ft. 

above    Floor. 


SPECIFICATIONS 

Location — 2  Units  per  Bay,  "Staggered," 
as  Shown  (128  Sq.  Ft.  per  Outlet). 

Mounting  Height— Good  Practice,  10  #  ft. 
above  Floor. 


75 


Design  No.  30.  Bays  lg  x  Jg  ft. 

Ceiling    Height— Not    Less    than    ^4.    ft. 

Caution:  Any  design  showing  less  than  2 
units  per  bay  is  not  recommended  for 
fine  operations  unless  at  least  2  rows 
of  units  are  installed.  Otherwise,  light 
will  not  reach  the  work  from  a  suf- 
ficient number  of  directions. 
Where  there  is  much  overhead  belting 
or  overhanging  machinery  to  cast 
troublesome  shadows,  use  Design  3b. 


SPECIFICATIONS 
Location — 1   Unit   per   Bay   as    Shown    (256 

Sq.    Ft.    per    Outlet). 
Mounting    Height — Good     Practice,     14    ft. 

above    Floor. 


Design  No.  ^a.  Bays  Jg  x  20  ft> 

Ceiling    Height    Not    Less    than    1Q    ft. 


SPECIFICATIONS 
Location — 4   Units  per   Bay   as    Shown    (80 

Sq.    Ft.    peil  Outlet). 
Mounting    Height — Good    Practice,    10    ft. 

above      Floor;       Preferably,      somewhat 

Higher. 


Design  No.  4.0.  Bays  Jg  x  20  ft* 

Ceiling    Height— Not    Less    than  ft. 


Wall  A 


SPECIFICATIONS 

Location — 4  and  2  Units  per  Bay  as  Shown 

(107    Sq.    Ft.   per   Outlet). 
Mounting  Height— Good   Practice,   10^    ft. 

above  Floor. 


Design  No.  40.  Bays   Jg  x  20  ft- 

Ceiling    Height— Not    Less    than    \       ft. 


.3* 


VlallA 


-*H^H  ?H 


fi  D  !!  °  iii 


1  f  i          h 

LailjJ- 

*T 


a 
"N 


a    i|    D-L't 

— • — r  .— -     L    — 

D  1    a  T  a 


p         D    ji    a 


i 


SPECIFICATIONS 

Location — 2  and  1  Units  per  Bay  as  Shown 

(213    Sq.    Ft.    per    Outlet). 
Mounting    Height— Good    Practice,    14    ft. 

above    Floor. 


Design  No.  4<1.  Bays  \Q  x  20  ft 

Ceiling    Height— Not    Less    than    \^    ft. 

Caution:  Any  design  showing  less  than  2 
units  per  bay  is  not  recommended  for 
fine  operations  unless  at  least  2  rows  of 
units  are  installed;  otherwise,  light  will 
not  reach  the  work  from  a  sufficent 
number  of  directions. 
Where  there  is  much  overhead  belting 
or  overhanging  machinery  to  cast 
troublesome  shaidows,  use  Design  4c. 


SPECIFICATIONS 

Location — 1    Unit  per   Bay   as   Shown    (320 

Sq.    Ft.    per    Outlet). 
Mounting   Height — Good    Practice,   16^    ft. 

above   Floor. 


Design   No.    fta..  Bays   20   X20   ft 

Ceiling    Height— Not    Less    than    JQ    ft 


Design  No.  fp>.  Bays  20  x  20  ft> 

Ceiling    Height— Not    Less    than    J2    ft- 


SPECIFICATIONS 

Location — 4  and  2  Units  per  Bay  as  Shown 

(133   Sq.    Ft.   per   Outlet). 
Mounting    Height — Good    Practice,    12    ft. 

above  Floor. 


Design  No.  gc.  Bays  20  x  20  fti 

Ceiling    Height— Not    Less    than    ^3    ft. 

Where  nteror  is  not  Ikely  to  be  subdi 
vided  into  smaller  rooms,  4,  2,  and  1 
units  per  bay  may  be  used  in  the  same 
manner  as  in  Design  6b.  There  will 
then  be  one  outlet  per  178  sq.  ft.  of 
floor  area. 


SPECIFICATIONS 

Location — 4  Units  per  Bay  as  Shown  (100 

Sq.    Ft.    per   Outlet). 
Mounting    Height — Good     Practice,     10    ft. 

above      Floor;      Preferably,       somewhat 

Higher. 


SPECIFICATIONS 

Location — 2  Units  per  Bay,  "Staggered," 
as  Shown  (200  Sq.  Ft.  per  Outlet). 

Mounting  Height — Good  Practice,  12  {/2  ft. 
above  Floor. 


77 


Design  No.  5<L  Bays  20  x  20  ftt 

Ceiling  Height— Not  Less  than  ^7  ft. 
Caution:  Any  design  showing  less  than  2 
units  per  bay  is  not  recommended  for 
fine  operations  unless  at  least  2  rows 
of  units  are  installed;  otherwise,  light 
will  not  reach  the  work  from  a  suf- 
ficient number  of  directions. 
Where  there  is  much  overhead  belting 
or  overhanging  machinery  to  cast 
troublesome  shadows,  use  Design  5c. 


SPECIFICATIONS 
Location — 1   Unit  per   Bay   as    Shown    (400 

Sq.    Ft.   per  Outlet). 
Mounting  Height — Good   Practice,   16^    ft. 

above    Floor. 


Design  No.  gb.  Bays  24  x  24  ftl 

Ceiling  Height— Not  tess  than  J£  ft. 
Caution:  Where  interior  is  likely  to  be 

subdivided,    a    system    similar    to    6c    is 

preferable. 

4-' 


D 

5t-  / 

D 

-^  f 

la           Q  i,'        a 
1                           K-/^ 

? 

I 

D 

Di-    n  1" 

ID           a_||        a 

D 

•i 

0\         ni 

r  T 

i  a          D  ll        n 

|| 

!           " 

a 

OJ,         D     " 

JO             O  ||          D 

) 

1                      il 

a 

a 

a 
=•-=-- 

D 

U- 

T  D 

i  a          a  ii        a 

i—  1— 

!a          a  |l        a 

-- 

Vj 

1                |l 

I!      1 

1                il 

SPECIFICATIONS 

Location — 4,  2,  and  1  Units  per  Bay  as 
Shown  (256  Sq.  Ft.  per  Outlet). 

Mounting  Height— Good  Practice  14  ft. 
above  Floor. 


Design  No.  ga.  Bays  24  x  24  ftl       Design  No.  gc.  Bays  24  x  24  ft 

Ceiling    Height— Not    Less    than    ^2    ft-       Ceiling    Height— Not    Less    than    ^5    ft. 


SPECIFICATIONS 
Location — 4   Units  per  Bay  as  Shown   (144 

Sq.   Ft.  per  Outlet). 
Mounting    Height — Good    Practice,    11    ft. 

above  Floor. 


SPECIFICATIONS 

Location — 2  Units  per  Bay,  "Staggered,"  as 
Shown  (288  Sq.  Ft.  per  Outlet). 

Mounting  Height— Good  Practice,  14^  ft. 
above  Floor. 


Design  No.   gd. 
Ceiling    Height—  Not 


Bays  24 
Less    tnan 


24 


ft. 


Caution:  Any  design,  showing  less  than  2 
units  per  bay  is  not  recommended  for 
fine  operations  unless  at  least  2  rows  of 
units  are  installed;  otherwise,  light  will 
not  reach  the  work  from  a  sufficient 
number  of  directions. 
Where  there  is  much  overhead  belting 
or  overhanging  machinery  to  cast 
troublesome  shadows,  use  Design  6c. 


SPECIFICATIONS 

Location — 1  Unit  per   Bay   as  Shown   (576 

Sq.    Ft.    per   Outlet). 
Mounting    Height— Good    Practice,    19    ft. 

above  Floor. 


AUXILIARY  LIGHTING  FOR  WORK  BENCHES 

In  general,  where  more  lighting  units  are  employed  than  one 
per  bay,  bench  lighting  can  be  adequately  cared  for  by  shifting 
the  outside  rows  of  units  nearer  to  the  walls  along  which  the 
benches  are  placed,  as  indicated  in  the  notes  accompanying  the 
designs.  This  means,  of  course,  that  the  spacing  distance  be- 
tween the  outside  row  of  units  and  the  next  is  greater  than  it 


Fig.    5- — Good    Arrangement    of   Auxiliary    Bench    Lighting    Units 

should  be,  and  the  illumination  at  points  between  the  two  rows  is 
correspondingly  reduced.  However,  since  this  area  of  low  illu- 
mination usually  covers  the  aisle  between  the  benches  and  the 
first  row  of  machines,  the  effect  is  usually  not  serious.  On  the 
ether  hand,  where  bays  are  large  and  only  one  unit  is  employed 
in  each  bay,  best  practice  usually  requires  auxiliary  bench  light- 
ing units.  A  typical  good  arrangement  of  auxiliary  units  is 
shown  in  the  sketch. 


79 


loo-watt  Bowl-Enameled  MAZDA  C  lamps  in  RLM  Standard 
Dome  reflectors,  spaced  8  ft.  apart  and  mounted  6  to  8  ft.  above 
the  bench  tops  will  provide  an  average  illumination  on  the  bench 
of  about  6  foot- candles;  this  is,  of  course,  in  addition  to  the  light 
received  from  the  general  overhead  system.  150- watt  lamps  so 
installed  will  provide  an  average  of  about  10  foot-candles. 

I5o-watt  Bowl-Enameled  MAZDA  C  lamps  in  RLM  Standard 
Dome  reflectors,  spaced  10  ft.  apart  and  mounted  7  to  10  ft.  above 
the  bench  tops  will  provide  an  average  illumination  on  the  bench 
of  about  6  foot-candles. 

The  distance  between  the  units  and  the  wall  is  governed  by 
the  width  of  the  benches.  The  units  should  be  so  located  that 
the  lamp  is  out  from  the  wall  a  distance  about  equal  to  the  width 
of  the  bench. 

115-VOLT  vs.  230-VOLT  MAZDA  LAMPS 

It  is  true  of  electrical  apparatus  in  general  that  as  the  voltage 
tor  which  it  is  designed  increases  beyond  certain  limits,  the  dif- 
ficulties of  manufacture  are  multiplied.  These  difficulties  are 
more  easily  overcome  in  some  types  of  apparatus  than  in  others. 
There  is  no  difficulty  in  manufacturing  motors  or  generators  for 
220-250  volt  service  Which  will  operate  at  as  high  an  efficiency 
and  will  give  as  satisfactory  service  as  those  manufactured  for 
110-125  volt  service.  The  limiting  voltage  for  incandescent 
lamps  is  lower,  and  it  has  not  been  found  possible  as  yet  to  man- 
ufacture for  voltages  ranging  between  220  and  250  volts  with  re- 
sults as  good  as  for  110-125  volt  service.  In  order  that  the  na- 
ture of  the  difficulties  may  be  more  readily  understood,  a  few 
are  discussed  in  the  following  paragraphs  : 

220-250  VOLT  LAMPS 

In  Fig.  6  are  shown  to  scale  a  4O-watt  n5-volt  lamp  and  a 
40-watt  230-volt  lamp.  The  filament  of  the  23O-volt  lamp  is  of 
necessity  1.7  times  as  long  as  that  of  the  ii5-volt  lamp.  For  this 
long  filament,  17  supports  are  needed  to  keep  the  filament  strands 
separated,  whereas  9  suffice  for  the  shorter  filament.  Each  sup- 
port draws  a  small  quantity  of  energy  which  escapes  from  the 
bulb  as  radiant  heat  and  is  lost;  and,  even  with  17  supports,  the 

80 


strands  of  the  23o-volt  filament  have  a  greater  tendency  to  lock 
together  and  short-circuit  a  portion  of  the  filament.  When  such 
mterlocking  occurs,  the  portion  of  the  filament  which  burns  re- 
ceives more  than  normal  current,  and  premature  failure  of  the 
Limp  results. 


ii5-Volt  Lamp 


230- Volt  Lamp 


Fig.    6 — 40  Watt    iiS-Volt,   and   40   Watt   230-Volt    MAZDA    Lamps. 
230- Volt  Lamp  has  a  Longer  Filament  and  Requires  8 
Additional  Supports.     Illustrations   One-Half  Scale 


The 


The  maximum  voltage  existing  between  supports  in  the  115- 
volt  lamp  is  approximately  92  volts.  The  supports  as  they  are 
held  in  the  "button"  on  the  center  rod  are  separated  about  0.06 
inch.  In  the  23O-volt  lamp,  the  maximum  voltage  between  sup- 
ports is  about  204  volts,  and,  since  the  distance  between  supports 
is  almost  exactly  the  same,  a  greater  current  flow  through  the 
glass  between  supports  takes  place.  Likewise,  a  greater  flow 
rakes  place  between  the  points  where  the  leading-in  wires,  with 
almost  the  entire  230  volts  difference  in  pressure  between  them, 
are  sealed  into  the  stem  glass.  The  increase  in  heat,  and,  on  di- 

81 


rect  current  particularly,  the  more  rapid  formation  of  electrolytic 
products,  which  result  from  the  greater  current  flow,  seriously 
affect  the  life  of  the  lamp. 

It  is  not  practical  to  employ  larger  buttons  than  are  at  pres- 
ent used  in  23<D-volt  lamps  and  in  this  way  permit  greater  spacing 
between  supports  because  of  the  fact  that  as  their  size  is  in- 
creased the  mechanical  strength  of  the  mount  is  reduced  unless 
a  thick  center  rod  is  used.  If  a  thick  center  rod  is  used,  the 
connection  with  the  stem  is  more  likely  to  be  faulty  and  unable 
to  resist  a  sudden  jar  or  shock.  The  center  rod  must  be  of  a 
r-ize  neither  too  large  nor  too  small  if  the  lamp  is  to  possess  max- 
imum strength. 

Even  with  the  high  degree  of  vacuum  existing  in  incan- 
descent lamps,  a  pressure  of  approximately  230  volts  between 
the  first  and  last  strands  of  filament  is  sufficient  to  produce  a 
current  transfer  through  the  residual  atmosphere  in  the  bulb  of 
considerably  more  moment  than  that  occurring  in  H5-volt  lamps. 
On  direct  current  particularly  is  the  effect  of  this  transfer  ob- 
jectionable, for,  in  some  cases,  the  continual  discharge  heats  the 
residual  atmosphere  to  a  point  where  it  becomes  a  sufficiently 
good  conductor  to  allow  an  arc  to  form  between  the  filament 
strands ;  this  arc  travels  rapidly  toward  the  base  of  the  lamp,  and 
ruptures  the  stem. 

The  filaments  of  the  two  lamps  shown  in  Fig.  6  have  a  cross- 
sectional  area  ratio  of  approximately  4  to  9,  the  23O-volt  filament 
being,  of  course,  the  smaller.  Aside  from  the  difficulties  of  draw- 
ing, and  working  with,  the  finer  filament,  there  is  the  disadvant- 
age that  small  filaments  must  be  operated  at  lower  temperatures 
if  they  are  to  show  a  life  performance  equal  to  that  of  large  fila- 
ments. The  light  which  a  filament  gives  is  dependent  upon  the 
temperature  at  which  it  operates;  for  this  reason,  as  Well  as  for 
those  previously  mentioned,  23O-volt  lamps  are.  less  efficient  than 
Ti5-volt  lamps  of  corresponding  wattage. 

TWO  LAMPS  IN  SERIES  ON  220-250  VOLTS 

In  order  to  profit  by  the  advantages  of  lamps  of  the  110-125 
volt  class,  the  practice  of  operating  two  lamps  in  series  across 
the  220-250  volt  lines  has  met  with  favor  in  many  industrial  in- 
stallations, where  severe  operating  conditions  and  long  hours 

82 


of  service  make  the  use  of  the  more  rugged,  less  expensive,  and 
more  efficient  low-voltage  lamp  particularly  attractive.  Under 
these  circumstances,  however,  slightly  less  than  normal  life  is  to 
be  expected  from  the  lamps,  for  although  two  new  lamps  usually 
operate  satisfactorily  in  series,  one  lamp  naturally  fails  sooner 
than  the  other,  and  when  a  replacement  is  made,  the  resistance 
of  the  two  lamps  will  be  higher  than  that  of  two  new  lamps  and 
less  than  that  of  two  old  ones,  for  the  resistance  of  lamps  in- 
creases with  burning.  H'ence,  the  new  lamp  will  receive  slightly 
less  than  normal  current  and  will  give  less  than  normal  candle- 
power,  while  the  old  lamp  will  be  forced  to  carry  a  somewhat 
heavier  current  than  it  would  normally  carry  at  that  period  of 
its  life  and  will,  therefore,  fail  earlier  than  it  otherwise  would. 

A  more  serious  disadvantage  of  operating  two  lamps  in  series 
is  that  the  failure  of  either  lamp  means  the  outage  of  both ;  thus 
a  relatively  large  area  is  left  without  sufficient  light  and  the  time 
of  several  persons  may  be  lost  while  the  defective  lamp  is  being 
located  and  the  replacement  made.  Obviously,  in  industrial 
plants  and  shops,  accident  risk  under  these  conditions  is  in- 
creased over  that  when  only  one  lamp  is  out. 


Fig.   7 — Typical    Balancer   Apparatus 
Motor-Generator  Set  on  Left;  Balancer  Coil  on  Right 

PROVIDING  110-125  VOLTS  FROM  220-250  VOLT 
CIRCUITS 

Few  are  the  modern  installations,  at  least  of  any  size,  where 
provision  is  not  made  for  supplying  110125  volts  for  the  lighting 
circuits.  The  larger  installations  often  generate  alternating  cur- 
rent which  is,  of  course,  readily  transformed  to  110-125  volts  for 
lighting.  The  energy  needed  by  such  apparatus  as  requires  di- 

83 


rect  current  is  obtained  by  converting  the  alternating  current  to 
direct  current.  In  new  plants  in  which  direct  current  is  gener- 
£ted  and  maximum  flexibility  in  the  control  of  motor  speeds  is 
desirable,  or  where  the  lighting  load  is  a  considerable  portion  of 
the  total  load,  the  present  practice  is  to  install  a  3-wire  gener- 
ator, which  provides  between  the  third  wire  and  either  main,  half 
the  main  line  voltage.  Where  the  lighting  load  is  a  small  pro- 
portion of  a  large  total  load  and  a  very  flexible  motor  speed  con- 
irol  is  not  essential,  the  installation  of  a  balancer  set  will,  in  gen- 
eral, provide  greater  economy. 

The  largest  field  of  the  220-250  volt  lamp  is,  then,  in  plants 
where  220-250  volt  circuits  are  already  used  for  lighting  circuits. 
In  such  cases,  except  for  very  small  installations,  the  most  satis- 
factory and  the  most  economical  lighting  results  are  secured  by 
providing  110-125  volt  circuits  by  placing  a  balancer  between  the 
220-250  volt  lighting  feeders  and  running  a  third,  or  neutral,  wire 
to  the  main  distributing  points.  The  purpose  of  the  balancer  is 
to  maintain  equal  voltages  on  the  two  sides  of  the  3-wire  circuit 
despite  unequal  loading.  For  alternating-current  circuits,  a  sim- 
ple balancer  coil  suffices ;  for  direct-current,  a  small  mechanic- 
ally coupled  shunt  or  compound  wound  motor-generator  set  is 
commonly  used.  Typical  apparatus  is  shown  in  Fig.  7. 

In  Fig.  8  is  shown  the  wiring  diagram  of  a  typical  23O-volt 
lighting  circuit.  Attention  is  called  to  the  fact  that  power  re- 
quirements have  been  cared  for  by  the  installation  of  a  separate 


UGHTIH6  filHU. 


Fig.  8 — Wiring  Diagram  of  Typical  230-Volt  Lighting  Circuit 

power  circuit.  This  practice  is  to  be  encouraged,  for  not  only 
are  fluctuations  in  voltage  caused  by  the  starting  of  motors  or 
by  the  sudden  shifting  of  heavy  loads  confined  at  least  in  part  to 
the  power  circuit  and  their  effect  upon  lamp  performance  thus 


reduced,  but  trouble  in  the  power  circuit  is  less  likely  to  cut  off 
the  illumination  of  the  plant  at  a  time  when  light  is  urgently 
needed. 

Figures  9  and  10  show  a  method  of  connecting  the  balancer  for 
adapting  the  23O-volt  circuits  to  H5-volt  lamps.  The  motor- 
generator  set,  or  the  balancer  coil,  is  connected  between  the  230- 
volt  mains,  and  a  neutral  wire  is  run  to  the  panel  boxes.  The 
power  load  connections  require  no  alterations.  Three-wire  pan- 
els can  usually  be  substituted  for  2-wire  at  moderate  expense; 
or,  if  thought  advisable,  a  3-pole  switch  may  be  substituted  for 
the  2-pole  in  existing  boxes  and  a  small  section  removed  from 
the  center  of  one  of  the  bus  rods.  The  two  outside  wires  are 
then  connected,  through  the  switch,  to  opposite  ends  of  the  split 
bus,  and  the  neutral  is  connected  to  the  continuous  bus  rod. 

For  the  sake  of  clearness,  a  simplified  diagram  showing  the 
important  connections  is  given  in  Fig.  n.  As  long  as  the  lamp 
loads  on  each  side  of  the  neutral  wire  are  equal,  or  balanced,  all 


nfvO    Q    Q 


Fig.  9 — A  Method  of  Connecting  Motor-Generator  Set  in  Direct-Current 

Circuit 


e. 

itt 

*lp  , 

!*&  '  6    ft 

,,gt§  —  3  —  ft  — 

-i 

( 

//«v 

//** 

Fig.     10 — A     Method     of     Connecting     Balancer     Coil     in     Single-Phase 

Alternating-Current    Circuit.    Where   Three-Phase    Lighting    Circuits 

are  Used,  Balancer  Coils  May  be  Connected  in  Each  Phase, 

but    the    Neutral    Points    Cannot    be    Grounded 

85 


the  current  which  flows  through  one  circuit  of  lamps  will  flow 
through  the  other,  the  23<>volts  will  automatically  divide  into 
H5-volts  across  each  lamp  circuit,  and  the  lamps  will  operate  at 
normal  voltage.  If  the  load  becomes  unbalanced,  the  side  hav- 
ing the  greater  load  will  have  less  resistance,  and  the  tendency 
will  be  for  the  voltage  to  divide  unequally  between  the  two  cir- 
cuits, the  voltage  across  the  heavily  loaded  side  becoming  less 
than  half  the  23O-volts  impressed  across  the  two  circuits.  If  this 
condition  obtained,  the  lamps  in  the  heavily  loaded  branch  would 
receive  less  than  normal  current  and  wlould  give  less  than  their 
normal  candle-power,  whereas  those  in  the  lightly  loaded  side 
would  receive  more  than  normal  current  and  would  burn  out  at 
less  than  rated  life.  However,  the  balancer  set  takes  care  of  this 
unbalancing.  Under  conditions  of  perfectly  balanced  load,  the 
two  machines  composing  the  motor-generator  set  run  idly  as 
motors,  taking  only  enough  energy  to  offset  the  no-load  losses. 


Fig.   ii — Simplified  Wiring   Diagram  of  Balancer   Set   Installation 

The  instant  that  the  load  becomes  unbalanced  and  the  voltage 
between  one  main  and  the  neutral  starts  to  fall  below  the  volt- 
age between  the  other  main  and  the  neutral,  the  tendency  of  the 
machine  on  the  low  voltage  side  is  to  slow  down  and  run  as  a 
motor  the  same  as  before  the  unbalancing  occurred.  This  is  pre- 
vented, however,  because  of  the  mechanical  connection  between 
the  two  machines,  and,  since  the  generated  voltage  of  the  ma- 
chine on  the  low-voltage  side  is  higher  than  the  voltage  im- 
pressed across  its  armature,  it  becomes,  automatically,  a  gener- 
ator, and,  within  its  capacity,  holds  the  voltage  of  the  heavily 
loaded  circuit  at  normal  or  nearly  so.  The  best  regulation  is  se- 
cured by  cross  connecting  the  fields  of  the  machines — that  is,  by 
connecting  the  field  for  one  armature  across  the  circuits  of  the 
other  armature  and  vice  versa. 


86 


The  current  which  the  heavily  loaded  side  carries  in  excess  of 
that  flowing  through  the  lightly  loaded  side  must  be  earned  by 
the  neutral.  This  neutral  current  divides  at  the  motor-generator 
set,  half  of  it,  plus  the  current  necessary  to  offset  the  losses  ot 
the  generator,  flowing  through  the  motor  and  the  remainder  flow- 
ing through  the  generator.  If  it  is  considered  advisable  to  pro- 
tect the  balancer  against  possible  overload,  a  circuit  breaker  may 
be  arranged  to  open  both  sides  of  the  circuit  between  the  bal- 
ancer and  the  source  of  supply  or  to  open  all  three  circuits  be- 
tween the  balancer  and  the  lamp  load;  the  precautions  taken  to 
guard  against  a  break  in  the  neutral  of  any  3-wire  system  should, 
of  course,  be  applied. 

The  action  of  a  balancer  coil  for  alternating-current  circuts  is 
very  similar  to  that  of  the  motor-generator  set.  The  coil  is  sim- 
ply a  23O-volt  auto-transformer  with  a  mid-voltage  tap.  As  long 
as  the  load  is  balanced,  the  coil  floats  on  the  line.  When  the  load 
becomes  unbalanced,  the  voltage  tends  to  rise  on  one  half  of  the 
coil  and  tends  to  drop  on  the  other.  Since  both  halves  of  the 
coil  are  on  the  same  magnetic  core,  the  voltages  of  the  two 
halves,  within  the  capacity  of  the  coil,  must  be  almost  exactly 
equal.  Hence,  the  voltages  of  the  two  lamp  circuits  are  main- 
tained nearly  equal. 

Since  the  current  which  the  balancer  must  carry  is  determined 
by  the  degree  of  unbalancing,  the  capacity  of  the  apparatus  re- 
quired in  any  given  case  depends  upon  the  magnitude  of  the 
lighting  load  and  upon  how  nearly  the  conditions  of  installation 
will  allow  the  circuits  in  the  panel  boxes  to  be  made  to  balance. 
Obviously,  the  greater  the  number  of  properly  connected  cir- 
cuits, the  smaller  the  chance  for  serious  unbalancing  to  occur. 
In  practice,  the  size  of  the  balancer  installed  ranges  from  about 
TO  per  cent,  of  the  total  connected  load  to  20  or  even  25  per  cent., 
depending  upon  the  size  of  the  lighting  load  and  upon  how  well 
the  circuits  may  be  divided.  The  capacity  of  the  balancer  set  as  used 
here  is  in  terms  of  the  current  flowing  in  either  machine  multi- 
plied by  the  total  impressed  voltage  of  220-250  volts,  or  the  cur- 
rent flowing  in  the  neutral  multiplied  by  half  the  impressed  volt- 
age. 


In  addition  to  effecting  maximum  lighting  economy  and  ob- 
taining superior  service  performance,  the  user  of  110-125  volt 


lamps  receives  the  benefits  resulting  from  the  use  of  a.  more  high- 
ly standardized  product.  Lamps  of  the  220-250  volt  range  are 
manufactured  primarily  to  supply  a  small  demand  which  does  not 
justify  the  stocking  of  quantities  of  lamps  to  fill  emergency  re- 
quirements. Furthermore,  improvements  are  less  readily  incor- 
porated because  of  the  greater  manufacturing  difficulties  present- 
ed by  high-voltage  conditions. 


88 


PART  V 

LIGHTING  OF  OFFICE  BUILDINGS  AND 
DRAFTING  ROOMS 

Introductory 

With  too  low  an  intensity  of  lighting  the  eye  is  soon  fatigued, 
particularly  when  engaged  in  clerical  work.  With  glaring  light 
sources  or  glaring  reflections  from  the  work  or  surroundings, 
the  efficiency  is  seriously  impaired.  With  dancing  or  shifting 
shadows  on  the  typewriter  or  ledger,  eye  strain  is  introduced. 
These  effects  are  particularly  serious  in  the  clerical  or  steno- 
graphic office  where  a  high  percentage  of  women  are  employed, 
lor  they  are  by  nature  particularly  sensitive  to  such  effects. 

Properly  installed  high  intensity  lighting  in  the  office  will 
increase  production  and  reduce  the  number  of  absentees. 

A  careful  consideration  of  the  subject  shows  past  standards 
of  intensity  to  be  too  low.  An  analysis  of  the  standards  recom- 
mended in  typical  textbooks  and  handbooks  shows  the  average 
values  set  down  as  desirable  to  be  between  three  and  four  foot- 
candles. 

It  is  possible,  of  course,  to  see  to  read  or  typewrite  with  less 
than  one  half  foot-candle,  but  severe  eye  strain  is  introduced,  and 
no  one  would  think  of  insisting  on  prolonged  work  under  such 
conditions.  Where,  then,  is  the  economic  or  critical  limit  to  in- 
tensity? One  hesitates  to  say,  and  can  merely  report  that  the 
most  progressive  firms  are  using,  and  the  leading  specialists  are 
recommending,  from  10  to  15  foot-candles  for  general  clerical 
work.  What  the  standard  will  be  a  decade  from  now  cannot  be 
accurately  foretold. 

One  often  hears  the  criticism  that  a  certain  place  is  over- 
lighted,  and  a  much  quoted  report  of  some  medical  men  who  in- 
vestigated office  lighting  conditions  in  lower  New  York  City, 
characterized  the  majority  of  them  as  "over-lighted."  A  sub- 
sequent casual  investigation  revealed  this  same  general  group 
of  buildings  to  be  even  below  the  standards  then  prevailing  for 
good  office  lighting. 

Glare  is  the  element  of  lighting  which  causes  the  layman  to 
refer  to  a  place  as  over-lighted.  These  offices  were  in  general 
glaringly  lighted.  Glare  is  the  element  we  must  guard  against 
if  the  advantages  of  higher  levels  of  illumination  are  to  be 
realized. 

89 


Method  of  Lighting 

A  few  years  ago  each  desk  had  a  portable  lamp  directly  above 
it  and  a  few  overhead  units.  This  is  what  is  termed  a  combina- 
tion of  local  and  general  illumination.  It  was  a  necessary  con- 
dition, since  the  lamps  were  not  efficient  enough  to  warrant 
supplying  a  sufficiently  high  intensity  throughout  the  entire 


Night  View  of  Totally  Indirect  Lighting  in  a  Small  Private   Office.     In 

this   installation   each    outlet    supplies    3    75-watt    MAZDA    C   lamps 

which    are    placed    in    inverted    mirrored-glass    reflectors 

concealed  in  a   spun  metal  housing.     The  intensity 

of  illumination  is  approximately  9  foot-candles 

room.  An  office  with  a  multiplicity  of  drop  lights  is  unsightly, 
the  cost  of  wiring  is  high,  and  there  is  a  heavy  expense  when 
wiring  is  changed  as  the  position  of  the  desks  are  shifted.  The 
employees  are  likely  to  change  the  location  of  lamps  by  tying 
the  wire  to  some  stationary  object,  a  practice  which  is  objec- 
tionable from  a  standpoint  of  safety  and  forbidden  by  the  wiring 
codes. 

Local  lighting  is  objectionable  as  there  is  a  great  liability  of 
glaring  reflections  from  the  desk  surfaces  and  glazed  paper;  the 
clerk  loses  time  shifting  the  light  about,  breakage  of  lamps  is 
increased,  and  there  is  often  marked  contrast  between  the 
brightly  lighted  desk  area  and  the  rest  of  the  room  which  does 
not  make  an  efficient  condition.  Now,  therefore,  general  illu- 

00 


initiation  is  practically  standard.  Overhead  units  alone  are  used 
— lighting  the  whole  room  uniformly — so  placing  the  lamps  that 
they  are  well  out  of  the  ordinary  angle  of  view,  equipping  with 
diffusing  glassware,  and  arranging  them  in  such  a  manner  that 
dense  shadows  are  avoided.  This  scheme  also  permits  the  use 
of  larger  lamps,  which,  as  a  general  thing,  are  more  efficient 
than  the  smaller  sizes.  Since  fewer  outlets  are  required  the 
cost  of  wiring  is  reduced.  A  great  deal  of  careful  investigation 
nas  proved,  without  doubt,  that  general  illumination  is  a  real 
economy,  all  things  considered,  in  comparison  with  local  lighting. 
Comparison  of  Systems  of  Lighting 

Direct  lighting  with  efficient  reflectors  is  unquestionably  the 
most  economical,  as  far  as  current  consumption  is  concerned,  of 
the  three  methods,  for  with  it  the  color  of  walls  and  ceilings  have 
less  effect  on  the  resultant  illumination.  Direct  lighting,  if  im- 


Semi-Indirect  Lighting  in  Small  Office 

properly  arranged,  may  produce  glare  either  from  the  light 
sources  themselves  or  by  reflections  from  the  objects  lighted,  or 
it  may  distribute  the  light  unevenly  and  as  a  result  produce 
dense  shadows.  It  is  not  generally  as  decorative  as  the  other 
methods.  Nevertheless,  thousands  of  satisfactory  installations 
of  good  direct  office  lighting  are  to  be  seen,  employing  translu- 

91 


cent  glassware  rather  than  opaque  reflectors,  thus  avoiding  the 
undesirable  condition  of  a  dark  ceiling  and  the  gloomy  appear- 
ance of  the  room.  Many  forms  of  semi-enclosing  glassware  of 
the  direct  type  are  giving  very  satisfactory  service. 

Totally  indirect  lighting  is  probably  the  most  "fool-proof" 
from  the  standpoint  of  a  glaring  installation.    The  light  is  usually 


Semi-indirect  Installation  in  Small  Office 

evenly  distributed  and  comfortable.  Objections  have  been 
raised  that  there  is  a  total  absence  of  shadow,  making  the  room 
appear  flat.  If  the  system  is  properly  designed,  however,  this 
is  not  true. 

Semi-indirect  lighting  is  an  intermediate  practice;  it  is  more 
efficient  than  totally  indirect  and  much  better  for  the  eye  than  the 
average  direct  lighting  system.  Semi-indirect  lighting  is  net 
glaring  if  the  proper  unit  is  chosen;  it  can  be  made  very  deco- 
rative, the  light  is  quite  evenly  distributed,  and  such  shadows  as 
are  produced  are  very  soft  and  do  not  become  annoying.  The 
fact  that  the  place  where  the  light  originates  is  readily  discein- 
:ble,  has  a  psychological  effect  on  the  average  individual  and 
makes  many  people  feel  more  at  ease  under  semi-indirect  light- 
ing than  under  totally  indirect. 

92 


A  semi-indirect  unit,  first,  should  be  of  quite  dense  glass; 
in  other  words,  transmit  but  a  small  portion  of  the  light,  if  the 
best  conditions  for  the  eye  are  to  be  obtained.  If  light  density 
glass  is  used,  the  bowl  becomes  very  bright  and  the  system  loses 
many  of  its  advantages,  dropping  back  to  the  direct  lighting 
class  where  a  number  of  fairly  bright  objects  are  in  the  field  of 
vision. 

Second,  the  fixture  or  hanger  used  should  be  of  such  a  length 
and  the  socket  in  the  proper  relative  position  to  the  bowl  that 
the  light  is  directed  in  such  a  maner  as  to  illuminate  the  ceiling 
evenly.  Many  cases  can  be  noted  where  the  lamp  is  placed  too 
low  in  the  dish,  concentrating  the  emitted  light  in  a  fairly  narrow 
?ngle  resulting  in  a  ring  or  circle  of  very  bright  illumination  on 
the  ceiling  directly  above  the  unit  with  the  spaces  between  units 


Common    Sense    Office    Lighting    of    a    Modern    Type.      ISO-watt    clear 

MAZDA  C  lamps  are  used  on  loft,  centers,  4  outlets  per  bay. 

The  resultant  illumination  is  slightly  over  9  foot-candles 

comparatively  dark.  At  other  times  to  get  rid  of  this  effect, 
the  lamp  is  raised  so  high  that  from  some  parts  of  the  room  the 
filament  becomes  visible,  introducing  glare.  On  the  introduc- 
tion of  the  Mazda  C  lamp  with  its  rather  concentrated  filament, 
this  feature  became  of  more  importance  than  formerly. 

93 


Third,  the  glass  used  should  be  smooth  inside  and,  preferably, 
outside,  as  roughed  glass  collects  dirt  very  readily  and  is  difficult 
lo  clean.  Needless  to  say,  all  lighting  fixtures  should  be  regu- 
larly and  carefully  cleaned  to  keep  the  illuminating  efficiency 
at  a  maximum. 

Fourth,  the  means  of  suspension  of  the  bowl  should  be  such 
that  there  is  absolutely  no  danger  of  the  glassware  falling  and 
it  is  desirable  to  have  some  convenient  means  of  cleaning. 

The  primary  purpose  of  the  fixture  is  to  support  the  lamp  and 
glassware  and  in  most  commercial  installations  should  be  as 
simple  as  possible,  of  plain,  well  finished  metal.  In  a  decorative 
interior,  such  as  a  director's  office,  the  ornateness  of  the  fixture 
is  of  more  importance  and  its  artistic  value  should  be  given 
due  consideration. 

Fifth,  in  the  commercial  office  the  decorations  of  the  glass- 
ware, if  any,  should  be  very  simple,  for  any  appearance  of  ex- 
cessive ornateness  would  be  out  of  keeping  wjith  the  character 
of  the  room.  Deep  crevices  in  the  glass,  although  they  may  be 
decorative,  are  objectionable  from  the  standpoint  of  dust 
accumulation. 

With  indirect  or  semi-indirect  systems  it  is  very  essential 
that  the  ceiling  be  light  in  color,  white  or  slightly  cream,  to  se- 
cure the  maximum  efficiency  of  reflection. 

Spacing  of  Outlets 

In  practice  a  rough  general  rule,  "never  space  outlets  much 
further  apart  than  the  ceiling  height,"  works  out  quite  satis- 
factorily. 

In  planning  the  location  of  outlets,  it  is  desirable  to  space 
these  symmetrically  with  regard  to  the  bays  or  columns.  The 
number  of  outlets  per  bay  will,  as  stated  above,  depend  on  the 
ceiling  height.  Standard  construction  is  tending  toward  2O-foot 
bays  in  office  buildings  and  for  the  ordinary  heights  of  ceiling 
4  outlets  per  bay  are  to  be  preferred.  If  the  bays  run  larger 
than  this  it  is  often  advisable  to  increase  the  number  of  outlets 
to  6,  as  future  demands  may  necessitate  the  dividing  of  the  large 
space  into  two  or  more  small  offi'ces.  The  6  outlets  per  bay  ar- 
rangement often  meets  these  conditions  without  necessitating 
any  additional  wiring.  In  some  cases  additional  outlets  are  pro- 
vided, but  not  fitted  with  fixtures  (the  outlet  box  rnerely  being 
covered  with  a  neat  cap)  to  make  provisions  for  the  future  and 

94 


avoid     the     necessity     of     opening    the     ceiling    for  rewiring. 

In  cases  where  an  unsymmetrical  arrangement  of  outlets  is 
necessary,  they  should  be  located  relatively  nearer  the  windows 
than  the  inside  wall  for  the  predominating  light  will  then  come 
from  the  same  direction  as  daylight. 

In  wiring  large  offices  lamps  should  be  controlled  in  rows 
parallel  to  the  windows  rather  than  in  groups  perpendicular  to 
the  windows.  In  this  manner  the  center  of  a  wide  room  which 
has  the  first  demands  for  artificial  light,  can  be  turned  on  be- 
"ore  light  is  required  nearer  the  window. 


A  High  Intensity  of  Illumination  if  Provided  in  this  Room  by  300-watt 

Clear  MAZDA  C  Lamps  in  Deep  Bowl,  Dense  Opal,   Inverted 

Reflectors.      This    type    of    illumination    gives 

diffusion  and  eliminates  dense  shadows 

It  is  very  rarely  that  an  office  can  be  lighted  satisfactorily  by 
one  outlet,   and   even  a  small  clerical  office  should  have  from 
2  to  4  outlets,  depending  on  its  size. 
Wattage  Required 

Good  practice  in  office  lighting  where  equipment  employing 
clear  bulb  lamps  is  used  calls  for  from  \y2  to  3  watts  per  square 
foot  depending  upon  the  effectiveness  of  the  equipment  em- 
ployed, the  size  and  proportions  of  the  office,  the  color  of  the 
ceiling  and  walls,  etc.  Equipments  of  the  enclosing  light-direct- 
ing type  in  either  opal  or  prismatic  glass,  the  semi-enclosing 

95 


type,  and  the  semi  and  totally  indirect  type,  are  adapted  to  the 
use  of  either  clear  or  daylight  lamps.  The  use  of  daylight  lamps 
is  preferred  by  many  because  of  the  fact  that  the  artificial  light 
then  blends  with  daylight  and  the  transition  from  one  to  the 
other  is  made  less  noticeable.  Where  daylight  lamps  are  used, 
about  50  per  cent,  more  wattage  is  required  for  the  same  ilumina- 
tion,  than  is  required  where  clear-bulb  lamps  are  employed. 

In  small  rooms,  since  a  greater  proportion  of  the  light  striken 
the  walls,  a  smaller  proportion  of  the  illumination  will  be  ef- 
fective than  in  a  large  room  with  the  same  size  lamps  and  same 
equipment. 

For  private  offices,  it  is  often  very  satisfactory  to  provide  a 
relatively  low  intensity  of  general  illumination  by  some  deco- 
rative central  unit  and  use  a  localized  light  of  satisfactory  dc- 
sign  for  the  desk.  This  should  be  located  in  such  a  manner  ?.s 
to  prevent  glaring,  annoying  reflections.  In  any  office  where 
glass  tops  are  used  on  the  desks,  particular  attention  must  be 
paid  to  the  type  of  lighting  fixtures  to  avoid  reflections. 

Drafting  Rooms 

Although  the  lighting  requirements  of  the  drafting  room  are 
somewhat  exacting,  they  may  be  readily  met  if  due  care  be  taken 
in  the  selection  and  location  of  lighting  units.  The  ideal  con- 
dition is  an  even  distribution  of  well  diffused  light  of  a  high 
intensity.  Shadows  must  be  minimized  as  they  make  it  difficult 
to  follow  the  fine  lines  when  one  is  working  close  to  the  T 
square  or  triangle. 

A  high  intensity  of  illumination  is  necessary.  Five  foot- 
candles  is  the  minimum  and  should  be  supplied  only  for  rough 
work.  For  the  most  exacting  work,  such  as  tracing  from  blue 
prints,  from  10  to  20  foot-candles  will  be  required. 

The  discussion  given  under  office  lighting  applies  to  the 
drafting  room.  The  requirements  are  even  more  exacting  as  the 
work  is  of  a  higher  grade  and  must  be  accurate.  Semi-indirect 
systems,  where  dense  glass  is  employed,  or  totally  indirect  sys- 
tems, are  probably  the  best  suited,  using  from  1.5  to  3.5  watts 
per  square  foot. 

Direct  general  illumination  of  a  high  intensity  using  rather 
close-spaced  semi-enclosing  units  is  also  used,  where  the  ceilings 
are  so  dark  as  to  preclude  the  use  of  indirect  systems,  and  found 
satisfactory.  The  units  should  be  located  with  reference  to  the 

96 


drawing  tables  and  so  arranged  that  the  maximum  light  will 
come  from  the  proper  direction.  Lamps  must  be  hung  well  out 
of  the  angle  of  vision  and  every  effort  made  to  avoid  glare. 

In  both  the  direct  and  semi-indirect  systems  of  illumination 
due  note  must  be  taken  of  the  usual  arrangement  of  boards 
relative  to  the  windows,  locating  the  lamps  so  that,  as  far  as 
possible,  the  direction  of  predominant  light  is  the  same  as  that 
of  daylight. 

A  system  which  is  quite  frequently  found  is  the  use  of  a  dif- 
fused general  illumination  (i  to  2  foot-candles)  supplemented 


Lighting  of  the  Drafting  Room 

by  a  local  lamp  for  each  drawing  board.  This  unit  may  be  of 
several  varieties,  fixed  or  movable,  attached  to  the  wall  or  to 
the  drawing  board,  opaque  or  diffusing  reflector,  and  various 
sizes  of  lamps;  but  in  any  case  it  is  open  to  the  usual  objec- 
tions of  local  lamps,  namely,  liability  of  glaring  reflections,  loss 
of  time  in  shifting  the  lamps,  and  relatively  high  maintenance 
cost. 

Tracing  may  often  be  satisfactorily  accomplished  by  having 
the  top  of  the  tracing  table  made  of  etched  glass,  and  lamps 
with  suitable  reflectors  placed  below  the  glass,  illuminating  the 
work  from  beneath  rather  than  from  above, 


PART  VI 
SCHOOL  LIGHTING 

Dr.  Wm.  M.  Howe  of  the  .New  York  State  Department  ot 
Education,  states :  "I  believe  that,  in  time,  any  school  service 
mat  does  not  prevent  most  of  these  ocular  defects,  with  which 
we  are  meeting  so  often,  will  be  considered  inefficient  and  dere- 
lict in  its  duty  to  school  children.  There  is  something  intrinsic- 
ally wrong  in  any  educational  system  that  permits  from  eight  to 
fifteen  per  cent  of  our  children  to  acquire  defective  vision  within 
the  few  years  of  their  school  lives.  Few  children,  as  you  know, 
are  born  with  defective  eyes." 

Proper  lighting  of  the  school  house  should  not  be  considered 
an  expense  but  an  economy.  If,  due  to  defective  vision,  a  pupil 
is  forced  to  spend  one  extra  year  at  school,  the  cost  of  teaching 
this  one  student  for  a  longer  period  than  normally,  will  much 
more  than  offset  any  of  the  expenditures  necessary  for  proper 
lighting.  Statistics  reveal  that  these  cases  are  legion. 

Illumination  Values 

It  is  self-evident  that  the  proper  amount  of  light  must  be 
supplied  for  any  kind  of  work.  The  correct  foot-candles  are  nec- 
essary in  order  that  everything  which  is  to  be  seen  may  be 
eeen  clearly  and  without  fatigue.  No  matter  what  system  is 
used,  unless  enough  light  actually  reaches  the  desks,  then  the 
lighting  system  is  inadequate. 

The  following  table  indicates  the  minimum  intensity  of  illu- 
mination it  is  desirable  to  provide  in  the  school  house. 

Classroom    5 — 10  foot-candles  on  desks 

Study  Room    5 — 10  foot-candles  on  desks 

Office     5 — 10  foot-candles  on  desks 

Cloak  Room  i — 3     foot-candles  on  floor 

Corridor   2 — 4     foot-candles  on  floor 

Laboratory     6 — 12  foot-candles  on  tables 

Auditorium    4 — 8     foot-candles  on  floor 

Drawing    10 — 20  foot-candles  on  tables 

While  such  values  as  given  above  will  produce  satisfactory 
results,  the  higher,  rather  than  the  lower  intensities  are  recom- 
mended. With  the  higher  intensities,  an  increased  degree  of 
perception  is  obtained.  If  increased  production  in  industrial 
plants  and  offices  can  be  profitably  brought  about  by  high  level 
lighting,  why  should  not  increased  speed  and  accuracy  of  ac- 
complishment on  the  part  of  the  pupils  likewise  be  worth  while? 

98 


As  an  unfortunate  result  of  our  ecomonic  system,  students 
are  usually  compelled  to  work  under  less  light  than  is  provided 
in  industry  for  similar  operations.  In  reality,  more  light  is 
needed  because  the  pupil  in  the  process  of  learning  has  to  give 
rloser  visual  attention  than  a  workman  to  whom  a  process  be- 
comes more  or  less  automatic. 
Diffusion 

The  harmful  effects  of  glare  cannot  be  over  emphasized.  The 
jikelihood  of  glare  from  light  sources  is  becoming  greater  and 
greater  with  the  development  of  higher  efficiency  lamps  with 
their  increased  intrinsic  brightnesses. 

We  therefore  always  reduce  the  brilliancy  of  the  light  by 
means  of  diffusing  globes,  shades  or  reflectors  which  either  ef- 
fectively enlarge  the  light  sources  or  actually  hide  them  from 


Diffusion  also  softens  the  shadows  so  that  severe  contrasts 
are  less  likely  to  occur.  It  is  not  desirable,  however,  to  go  to 
such  an  extreme  diffusion  that  we  entirely  eliminate  shadows, 
for  they  are  very  essential  to  show  the  contour  or  shape  of  ob- 
jects. Over-diffusion  or  flat  illumination  is  trying  to  the  eyes 
and  unpleasant. 

Not  only  must  we  take  care  of  the  light  sources  themselves 
in  providing  diffusion,  but  the  walls  and  objects  in  the  room 
must  be  given  attention  as  well.  Dull  rather  than  polished  sur- 
faces are  desirable  here,  and  even  a  depolished  or  waxed  'finish 
is  more  desirable  than  varnished  or  highly  polished  surfaces  on 
the  desk  and  other  furniture,  as  the  latter  produce  mirrorlike 
effects  in  reflecting  the  light  sources. 

In  this  connection,  attention  should  also  be  given  to  the 
desirability  of  mat  rather  than  glossy  finished  paper  for  paper 
with  a  glossy  finish  likewise  reflects  light  in  an  annoying  manner. 

GENERAL  CONSIDERATIONS 

The  Classroom 

In  most  interiors  we  space  outlets  symmetrically  throughout 
the  room,  but  with  the  schoolroom,  as  with  the  machine  shop, 
the  shadow  effect  is  very  important,  so  we  have  the  maximum 
light  coming  slightly  forward  and  from  the  left  to  diminish  the 
head  and  hand  shadow's  ;  as  far  as  possible  the  direction  of  day- 
light is  imitated,  sometimes  much  improved. 

99 


To  accomplish  this  we  arrange  outlets  as  shown  in  Fig.  I, 
"favoring  the  window  side." 

More  outlets  are  required  for  direct  lighting  than  for  the  in- 
direct systems,  in  order  that  multi-directional  light  may  be  pro- 
vided. It  is  always  desirable  to  hang  units  as  high  as  possible 
to  keep  them  out  of  the  field  of  view.  No  lighting  units  should 
come  below  a  line  extended  from1  the  eye  of  a  student  in  the  rear 
seat  to  a  point  two  feet  above  the  blackboard. 


;t 

*o 

_  e'-o*  .[.  '?  —  ic'-o"  —  .  —  -4_  s'-o"-. 

ff"^ 
4-4 

YO*   n* 

Fig. 

WINDOW    9IOC    Of    ROOM 


•3Z'-0" 


Typical    Arrangement    of    Outlets    for    the    Average    Size    School    Room 
(24  x  32  ft).     The  Size  of  Lamp  Specified  Represents  Good  Practice 
Fulfilling    the    Intensity    Requirements    Set    Forth    in    the    Text. 
A — Four  2OO-Watt   Clear   MAZDA   C   Lamps   in   Dense   Glass 
Semi-Indirect  Units,  Totally  Indirect  Equipment  or  En- 
closing Diffusing  Globes.  B — Six  loo-Watt  Bowl  Enam- 
eled MAZDA  C  Lamps  in  Etched  Prismatic  or  Dense 
Opal    Deep    Bowl    Direct    Lighting    Reflectors 

Blackboards 

There  is  a  likelihood  of  glaring  reflections  from  blackboards 
and  they  should,  therefore,  always  have  mat  rather  than  pol- 
ished surfaces.  It  is  sometimes  possible  to  get  rid  of  this  re- 
flection by  tilting  the  boards  slightly.  Blackboards  on  which 
rolored  chalks  will  be  used  and  those  that  are  more  than  twenty 
feet  away  from  the  pupil  should  be  especially  lighted  to  an 
intensity  approximately  60  per  cent  higher  than  the  intensity  in 
the  rest  of  the  room.  This  can  be  accomplished  by  the  use 
nf  properly  screened  and  judiciously  placed  local  units  similar 
to  the  systems  commonly  used  on  outdoor  signs  and  billboards. 
For  clear  vision,  blackboards  should  not  be  located  between 
windows. 

Comparison  of  Various  Lighting  Systems 

Direct,    semi-indirect,   and   totally   indirect   systems   are    all 


100 


employed  for  school  lighting.  Each  has  certain  advantages  and 
disadvantages  which  are  outlined  below.  A  number  of  factors 
must  be  taken  into  consideration  which  may  be  briefly  stated  as 
below : 

Quality  of  illumination  produced. 
Convenience  of  maintenance. 
Appearance  of  the  installation. 
Efficiency  of  the  system. 
Ability  to  provide  the  desired  intensity. 
Cost  of  installation. 

Certain  systems  may  appear  to  be  most  desirable  from  the- 
oretical considerations,  but  may  not  work  out  well  in  practice. 
Obviously,  the  type  of  lighting  unit  to  select  is  the  one  which 
will  give  a  desirable  quality  of  illumination  in  as  efficient  a  man- 
ner as  possible,  over  a  long  period. 

The  proper  maintenance  of  a  lighting  system  in  any  class 
cf  service  is  of  very  great  importance.  Even  greater  emphasis 
must  be  laid  on  this  question  in  the  school,  for  supervision  is 
at  best  meager  and  periods  between  cleaning  are  of  consider- 
able length.  These  conditions  should  not  exist  but  neverthe- 
less, we  must  recognize  that  such  is  the  case  and  take  this  into 
consideration  when  planning  the  lighting. 

Totally  indirect  lighting  produces  a  very  high  quality  of 
illumination,  but  requires  a  relatively  large  wattage  for  a  given 
intensity.  With  such  a  system,  there  is  little  possibility  of  glare 
and  the  light  is  very  soft  and  comfortable  to  work  under.  Glar- 
ing reflections  are  at  a  minimum.  The  inverted  bowls,  however, 
tend  to  accumulate  considerable  dirt  and  unless  cleaned  fre- 
quently the  light  output  is  materially  reduced. 

Semi-indirect  lighting  is  an  intermediate  step,  most  of  the 
light  from  the  lamps  being  directed  to  the  ceiling,  with  a  slight 
amount  transmitted  through  the  glassware.  It  is  slightly  more 
efficient  than  totally  indirect  lighting,  the  resultant  illumina- 
tion is  well  diffused,  and  such  shadows  as  are  produced  are  very 
soft  and  do  not  cause  annoyance.  The  best  forms  of  semi- 
indirect  units  for  school  work  employ  dense  glass  or  some  other 
means  of  reducing  the  brightness  of  the  lighting  unit. 

Ther*  have  recently  appeared  on  the  market,  a  number  of 
totally  enclosing,  semi-indirect  units  which  are  relatively  easy 
to  clean  and  therefore  offer  special  advantages. 

101 


In  many  of  the  older  installations,  open  bottom,  direct  light- 
ing units  are  used.  Such  a  system  is  obviously  efficient  from 
the  standpoint  of  light  utilization,  but  the  diffusion  is  not  of  the 
highest  quality,  shadows  and  contrast  are  likely  to  be  rather  se- 
vere, and  direct  and  reflected  glare  become  serious,  particularly  if 
( lear  bulb  lamps  are  employed.  The  use  of  this  form  of  lighting 
is  only  advisable  where  costs  must  be  kept  at  a  minimum  and 


Class    Room   Lighting 

where  secondary  consideration  is  given  to  the  quality  of  illumi- 
i.ation. 

Where  direct  lighting  is  deemed  advisable,  dense  opal  or 
etched  prismatic  reflectors  should  be  used.  These  transmit  but 
a  small  portion  of  the  light,  and  they,  therefore,  are  not  very 
bright.  The  diffusing  bulb  or  bowl  enameled  Mazda  C  lamp 
should  always  be  employed  with  open  reflectors  in  preference  to 
the  clear  lamp,  as  these  finishes  produce  better  diffusion,  reduce 
reflected  glare  and  soften  'shadows. 

The  flat  type  reflectors  should  never  be  used  in  a  schoolroom, 
lor  it  is  almost  Impossible  to  conceal  the  filament  from  view  when 
using  this  style  of  shade.  Opaque  reflectors  are,  of  course,  gen- 
erally unsuited,  as  the  ceiling  would  be  very  dark  when  these 
are  used. 

IO2 


In  view  of  the  above  analysis,  the  enclosing,  diffusing,  direct 
lighting  luminaire  seems  to  be,  at  the  present  state  of  the  art, 
the  most  generally  applicable  equipment  for  classroom  lighting. 
]f  the  proper  type  is  chosen,  a  well  diffused  illumination,  quite 
free  from  direct  or  reflected  glare,  is  produced.  Although  the 
major  portion  of  the  light  is  directed  downward,  a  considerable 
amount  is  transmitted  upward,  thus  giving  a  cheerful  appearance 
to  the  room  and  a  character  of  illumination  closely  akin  to  that 
produced  by  semi-indirect  units.  It  is  apparent  that  such  equip- 
ment does  not  depreciate  as  rapidly  with  the  accumulation  of  dirt 
oS  do  other  fixtures  producing  the  same  general  quality  of  illu- 
mination. This  should  not  be  taken  to  mean  that  cleaning  can 
be  neglected,  for  it  is  always  of  prime  importance. 

A  typical  specification  for  a  suitable  school  lighting  unit  of 
ihe  diffusing  enclosing  type,  might  be  drawn  up  as  follows: 


Class   Room    Lighting 

The  glassware  shall  be  of  thin  blown- opal  or  cased  glass  giv- 
ing good  diffusion  with  low  absorption. 

It  shall  be  of  such  a  size  that  the  brightness,  with  recom- 
mended size  of  lamp,  is  not  uncomfortable  even  when  the  unit  is 
viewed  for  long  periods  of  time. 

It  shall  be  of  such  a  shape  that  a  horizontal  section  is  greater 
than  a  vertical  section. 

103 


The  supporting  holder  shall  be  sufficiently  strong  and  of  such 
a  type  as  to  preclude  any  possibility  of  the  glassware  falling. 

The  method  of  support  shall  be  such  that  the  globe  can  be 
icadily  removed  for  cleaning. 

Similar  specifications  can  be  readily  drafted  for  other  forms 
of  equipment. 

Corridor 

The  lighting  can  be  accomplished  with  relatively  low  watt- 
age lamps,  on  fairly  wide  spacings,  provided  diffusing  glassware 
is  employed.  Uniform  illumination  is  not  necessarily  essential. 
Smaller  sizes  of  the  same  general  type  of  equipment  as  used  in 
the  classroom  can  be  utilized  for  the  corridor.  A  row  of  outlets, 
symmetrically  spaced  along  the  center  line  of  the  ceiling,  is  gen- 
erally to  be  preferred,  although  sometimes  the  structure  is  such 
as  to  make  ceiling  outlets  inadvisable.  In  these  cases,  brackets 
or  wall  fixtures  must  be  employed.  In  general,  75  watt  Mazda  C 
lamps  on  15  foot  centers  are  adequate.  With  corridors  over  8 
feet  wide,  larger  lamps  are  necessary. 

Laboratory 

The  laboratory  requires  a  relative  high  level  of  illumination 
m  order  that  the  progress  of  experiments  may  be  carefully 
watched.  The  general  layout  suggested  for  the  classroom  is  sat- 
isfactory for  the  laboratory.  In  the  chemical  department,  how- 
ever, acid  fumes  will  attack  metal  parts  of  ordinary  fixtures  and 
soon  make  them  useless.  For  this  reason  porcelain  enameled  re- 
flectors and  porcelain  receptacles  or  sockets  are  well  adapted. 
The  RLM  standard  dome  reflector  with  bowl  enameled  Mazda  C 
lamp  makes  an  excellent  lighting  device  for  such  rooms.  It  is 
efficient,  durable,  inexpensive,  and  diffuses  the  light  satisfactorily. 

Auxiliary  Outlets 

The  stereopticon  and  motion  picture  machines,  as  well  as 
many  electrical  devices,  are  becoming  important  factors  in  our 
educational  system.  Every  classroom  should  have  an  outlet  to 
which  these  can  be  attached. 

The  auditorium  should  have  a  well  equipped  motion  picture 
booth  for  exhibiting  standard  films.  The  Mazda  lamp  for  motion 
picture  projection,  with  its  economy  and  convenience  of  opera- 
tion, is  a  boon  to  the  school. 

104 


PART  VII 
RESIDENCE  LIGHTING 

introduction 

When  w;e  realize  the  amount  of  time  that  we  are  dependent  on 
artificial  light,  it  is  not  surprising  that  devices  which  give  proper 
illumination  are  receiving  more  and  more  attention.  In  the 
home,  the  useful  and  decorative  phases  of  lighting  must  be  com- 
bined, neither  one  being  emphasized  at  the  expense  of  the  other. 
The  decoration  of  a  room  may  be  absolutely  spoiled  or  given  the 
final  touch  of  perfection  by  the  lighting  effect.  Time,  care,  and 
considerable  money  are  spent  in  establishing  harmony  of  the 
furniture,  hangings,  and  room  finish,  and  avoiding  any  discord 
between  the  styles  of  furniture  used.  But  of  what  use  are  these 
refinements  in  the  matter  of  the  decorations  and  furniture  unless 
the  lighting  is  such  that  these  elements  can  be  appreciated?  It 
must  be  remembered  that,  as  a  general  rule,  it  is  during  the 
hours  when  we  need  artificial  illumination  that  we  wish  the  house 
to  appear  at  its  best.  Comfortable  lighting  makes  pleasant  sur- 
roundings enjoyable,  but  with  poor  illumination  the  carefully 
planned  details  of  the  room  are  ineffective. 

Fortunately,  with  the  wide  range  of  sizes  of  efficient  lamps 
and  the  number  of  styles  of  standard  lighting  equipment  available 
it  is  possible  to  have  extremely  effective  lighting.  The  intensity 
of  light  desired  for  any  particular  purpose  can  be  obtained  with- 
out the  objectionable  feature  mentioned  above.  No  longer  is  it 
necessary  to  have  only  one  light  source  in  a  room.  The  more 
reasonable  way  is  to  have  a  lighting  system  that  can  be  readily 
adapted  to  the  requirements  of  the  people  rather  than  making 
it  necessary  for  them  to  adapt  themselves  to  such  lighting  as 
happens  to  be  available. 

As  an  example  of  this,  let  us  consider  the  living  room  of  an 
average  home.  In  this  room  many  recreations  are  enjoyed. 
Reading  requires  more  light  than  talking,  but  music  is  more  en- 
joyable in  what  is  known  as  a  "half  light."  If  then,  we  are  able 
to  have  the  room  softly  lighted  by  decorative  table  lamps  with 
the  help  of  wall  brackets,  we  can  produce  a  general  atmosphere 
of  quiet  contentment,  the  portable  lamps  furnishing  illumination 
tor  those  reading  beside  them.  For  a  comfortable  game  of  bridge, 
it  is  a  necessity  that  each  player  be  able  to  see  his  cards  easily, 
without  holding  his  hand  to  avoid  shadows.  The  most  efficient 

105 


way  to  furnish  equal  light  for  all  is  to  make  use  of  a  ceiling 
himinaire  of  the  semi-indirect  type,  which  will  light  the  whole 
room  to  an  even  intensity.  The  advantages  of  variable  lighting 
are  readily  appreciated,  not  only  in  the  living  room,  but  in  all 
other  rooms  of  the  home. 
Systems  of  Lighting 

There  are  three  general  ways  of  lighting  a  room,  i.e.,  by  di- 
rect, totally  indirect,  or  semi-indirect  illumination.  With  lumi- 
naires  of  the  first  class,  shades  are  used  that  send  the  dominating 
light  directly  down  where  it  is  to  be  used.  The  dining  room 
dome,  the  shower  fixtures,  the  pendant  wall  brackets,  and  the  or- 
dinary table  lamp,  all  are  examples  of  this  type  of  lighting. 

Just  the  opposite  effect  is  obtained  by  using  the  indirect  sys- 
tem because,  in  that,  all  the  light  is  directed  to  the  ceiling  which 
in  turn  acts  as  a  large  reflector  and  distributes  the  light  through- 
out the  room.  No  dense  shadows  are  created  because  the  light, 
being  reflected  from  such  a  large  surface,  is  well  diffused.  This 
type  of  lighting  can  be  obtained  from  special  portable  lamps, 
with  inverted  reflectors  on  the  tops  of  bookcases  or  in  wall  urns, 
as  well  as  from  ceiling  luminaires. 

Now,  if  the  inverted  bowl  instead  of  being  opaque  allows 
i^ome  of  the  light  to  be  transmitted  through  it,  still  reflecting  a 
greater  portion  to  the  ceiling,  we  have  an  example  of  semi-indi- 
rect lighting,  another  form  of  this  being  a  translucent  reflector  on 
an  upright  wall  bracket. 
Kitchen 

The  unfortunate  part  of  the  ordinary  kitchen  luminaire  is 
its  inability  to  be  adapted  to  much  improvement.  The  combina- 
tion gas  and  electric  stem  luminaire  places  the  lamp  so  low  that 
the  only  thing  it  can  do  is  to  cast  the  shadow  of  the  worker  on 
the  work.  The  designer  of  such  a  luminaire  seems  to  have  the 
mistaken  idea  that  the  light  is  wanted  on  the  floor  in  the  center  of 
the  room  rather  than  on  the  stove  or  sink.  Then,  too,  the  glass- 
ware that  is  used  is  ineffective.  There  is  really  little  that  can  be 
done  to  improve  this  luminaire  save  by  the  substitution  of  diffus- 
ing bulbs  for  clear  lamps.  If  satisfactory  lighting  is  desired,  this 
luminaire  should  be  replaced  by  one  which  carries  the  lamp  close 
to  the  ceiling  and  is  furnished  with  a  glass  reflector  that  will  as- 
sist in  distributing  the  light  around  the  sides  of  the  room.  Of 
course,  if  the  room  is  large,  this  ceiling-  light  will  have  to  be  aided 
in  its  efforts  by  wall  brackets  in  the  darker  parts.  The  shades 

106 


used  should  be  of  dense  opal  glass  with  smooth,  easily  cleaned 
surfaces.     For  places  of  average   dimensions,   a  75-watt   white 


Typical   Luminaires   for   the   Kitchen   Which   Will    Provide    Suitable   Lighting 

if   Properly  Applied 

or  a  TOO- watt  bowl  enameled  MAZDA  C  lamp  in  an  8-in.  diameter 
reflector  should  be  used  in  the  ceiling  unit,  while  25-watt  all 
irosted  MAZDA  B  lamps  in  6-in.  reflectors  will  serve  on  the  brack- 
et luminaires.  Such  a  combination  will  do  away  with  objec- 
tionable glaring  reflections  that  a  bare  light  source  will  give 
when  bright  pans  are  used. 

When  the  ceiling  is  painted  a  light  color,  a  semi-direct  system 
of  lighting  is  effective.  With  this  installation,  only  the  ceiling 
Jnminaire  is  necessary  and  yet  the  shadows  are  reduced  to  a  mini- 
mum. A  loo-  or  I5o-watt  clear  MAZDA  C  lamp  in  such  a  lumi- 
naire  will  provide  adequate  intensity  in  the  typical  kitchen. 

A  wall  switch  near  the  doorway  is  a  mpst  desirable  feature, 
but  its  absence  will  not  prevent  the  use  of  a  luminaire  hung  out 
of  reach,  for  chain  pull  sockets  with  a  length  of  cord  and  lumi- 
nous indicator  may  be  used  to  control  the  light. 

Whatever  form  of  lighting  is  employed,  it  is  highly  important 
that  convenience  outlets  for  the  iron,  percolator,  or  fan  be  pro- 
vided. The  position  of  the  outlet  to  which  the  iron  will  be  con- 
nected merits  consideration'  and  should  be  such  that  the  mini- 
mum of  shadows  is  cast  on  the  board  both  in  the  daytime  and  at 
night. 

107 


Another  way  to  make  the  kitchen  as  comfortable  and  as  easy 
to  work  in  at  night  as  it  is  in  the  daytime,  is  by  the  use  of  Mazda 
daylight  lamps.  The  daylight  quality  of  the  light  not  only  makes 
a  cleaner  looking  kitchen,  but,  just  because  it  is  like  daylight, 
stains  are  more  readily  visible  and  therefore  the  kitchen  actually 
is  cleaner. 

Butler's  Pantry 

If  the  outlet  is  not  already  in  place,  it  is  preferable  to  have  it 
installed  directly  over  the  sink.  A  direct  lighting  opal  reflector, 
5O-watt  MAZDA  lamp,  close  ceiling  luminaire,  with  pull  chain 
socket,  may  well  be  used  here.  When  the  outlet  is  already  in 
the  center  of  the  room,  this  type  of  lighting  is  not  advisable  be- 
cuse  of  the  shadows  that  will  be  cast  by  the  worker  on  the  sink. 
Under  such  conditions,  semi-indirect  lighting  is  preferable  and  a 
harp  type  holder  may  be  used  that  suspends  an  opal  glass  re- 
flector under  the  lamp.  A  convenient  outlet  near  the  sink  is 
desirable  for  attaching  a  small  motor  for  polishing  silver  or 
other  time-saving  devices. 

Laundry  and  Work  Bench 

As  a  usual  practice,  the  washing  machine  is  installed  in  the 
basement  and  artificial  illumination  will  probably  be  necessary 
whenever  the  machine  is  used.  High  level  illumination  is  a  de- 
sirable factor  here  and  MAZDA  daylight  lamps  make  it  easier  to 
detect  stains  on  linen.  The  100-  or  I5o-watt  bowl  enameled 
MAZDA  C  lamps  in  RLM  Standard  dome  reflectors  make  an  effi- 
cient luminaire  giving  the  desirable  quality  of  diffusion  and  dis- 
tribution. The  type  of  direct  luminaires  suggested  for  the  kit- 
chen is  also  applicable  where  the  laundry  is  "finished  off." 

The  location  of  convenience  outlets  for  the  washing  machine 
and  ironer  should  be  considered  with  respect  to  the  position  of 
the  light  source.  For  hand  ironing,  an  outlet  on  a  drop  cord  is 
preferable  to  one  in  the  side  wall  or  baseboard  in  giving  greater 
latitude  in  the  work. 

The  lights  for  the  cellar  proper  should  be  so  distributed  as  to 
•"iluminate  the  foot  of  the  stairs,  the  furnace,  coal  bins,  and  cold 
pantries.  If  the  ceiling  is  finished  in  a  light  color,  flush  or  sur- 
face receptacles  with  diffusing  bulb,  low  wattage  lamps  without 
reflectors  will  give  a  wide  spread  of  light  at  a  low  cost  of  in- 
stallation. 

At  least  one  of  the  cellar  lights  should  be  controlled  from  the 

108 


head  of  the  stairs  and  it  is  desirable  to  have  some  sort  of  a  pilot 
device  to  indicate  whether  or  not  the  lamps  are  burning. 

Den  or  Sewing  Room 

The  lighting  requirements  of  these  two  rooms  are  so  similar 
that  they  can  well  be  discussed  together.  For  close  Work,  either 
m  sewing  or  keeping  records,  a  high  intensity  of  illumination  is 
necessary.  For  ordinary  purposes,  however,  we  do  not  want  to 
have  the  whole  room  as  light  as  this.  A  combination  of  lighting 
is  desirable,  a  central  diffusing  luminaire  to  furnish  general  illu- 
mination of  moderate  intensity,  and  a  portable  luminaire  for  the 
close  work. 


A  Simple  Means  of  Obtaining  Semi-indirect  Effects  from  a  Direct  Light 

ing  Luminaire  and  the  Efficient  RLM  Standard  Dome  Reflector 

for  Lighting  the  Basement  and  Garage.     The  porcelain 

enamel  resists  attacks  of  moisture 

Living  Room 

The  living  room  is  the  scene  of  the  social  life  of  the  house, 
and  the  lighting  of  such  a  room  should  receive  special  attention. 
It  must  be  agreeable  and  bring  out  the  especial  points  of  the  dec- 
orative scheme.  It  will  not  be  a  full  success  if  it  makes  people 
look  tired,  old,  or  unattractive,  by  bringing  out  sharp  facial  shad- 
ows. Into  this  room  novel  effect  may  be  introduced  that  vary 
the  monotony  of  ordinary  lighting.  Small  lamps  burning  inside 
translucent  vases  render  them  luminous  and  show  beauties  that 
would  otherwise  not  be  noticed.  The  possibilities  in  the  way  of 
special  effects  can  be  utilized  only  when  an  adequate  number  of 
convenience  outlets  are  available.  Ingenuity  will  soon  indicate 
many  expedients  by  means  of  which  the  little  touches  of  color, 


109 


that  aid  so  much  in  the  appearance  of  the  room,  can  be  intro- 
duced at  will. 

For  general  lighting,  when  only  one  outlet  is  available,  a 
semi-indirect  luminaire  will  more  nearly  meet  the  average  re- 
quirements than  any  one  type.  A  lamp  of  sufficient  size  can  then 
ie  used  to  furnish  the  necessary  intensity  and  the  light  will  be 
comfortable  and  devoid  of  glare,  provided  a  proper  design  is 
chosen. 

A  100-  or  150-watt  Mazda  C  Lamp  will  usually  provide  a  de- 


Adaptability    is    the    Keynote    of    the    Lighting    Shown    in    This    Room. 

ISO-watt    MAZDA   C   lamps   are   used   in   inverted   reflectors    in   the 

portables.    15-watt  all  frosted  MAZDA  lamps  in  the  brackets  are 

concealed  by  shields  harmonizing  with  the  wall  coverings 


sirable  intensity  of  illumination  with  semi-indirect  luminaires 
in  rooms  of  average  dimensions. 

There  are  innumerable  period  styles  of  luminaires  suitable  for 
the  living  room.  A  few  typical  examples  are  indicated  in  the  ac- 
companying sketches.  In  choosing  luminaires  of  this  nature,  the 
cardinal  points  in  regard  to  distribution  of  light,  contrast,  and 
direct  glare  must  be  kept  in  nuind.  Very  rarely  is  it  feasible  to 
use  lamps  without  some  sort  of  a  shade  or  diffusing  medium. 

With  a  suitable  number  of  wall  and  convenience  outlets  it  is" 

no 


good  practice  to  light  the  living  room  without  a  central  or  ceiling 
luminaire,  and,  in  this  event,  table  and  floor  lamps  may  be  used 
to  advantage. 


The   Styles  of  Portable  Lamps   Giving  Good  Results  Are   Innumerable. 
These  are  just  a  few  suggestions 


All  portable  lamps  should  be  chosen  with  particular  thought 
given  to  the  shades.  It  is  always  objectionable  to  be  forced  to 
look  at  a  lamo  and  the  shades  must  conceal  the  light  sources 
from  one  sitting  near  them.  The  materials  used  should  be 
dense  enough  that  the  filaments  do  not  show  through  and  as 
pointed  out  before,  it  is  always  desirable  to  use  diffusing  bulb 
lamps  in  any  kind  of  direct  luminaire.  With  skillful  selection, 
a  shade  will  become  an  integral  part  of  the  color  scheme  of  the 
room  in  the  evening,  as  it  is  during  the  day.  Sometimes,  however,  a 
color  is  used  that  harmonizes  well  enough  with  the  drapes  and 
iurniture  covering  but  when  the  shade  is  lighted,  the  effect  is 
far  from  desirable.  This  danger  is  most  likely  to  be  present 
when  green  or  blue  color  schemes  are  employed.  The  best 
solution  for  such  a  condition  is  to  have  the  exterior  layer  of 

in 


particularly  thin  material,  such  as  chiffon  or  georgette  crepe 
and  the  lining  a  rather  heavy  rose,  buff,  or  cream.  The  resultant 
light  will  be  toned  by  the  lining  and  ghastly  effects  eliminated. 

A  wall  switch  is  the  most  desirable  for  controlling  the  lights 
in  the  living  room,  and  it  is  generally  advisable  to  have  the 


A    Few    Styles    of    Direct,    Semi-Indirect    and    Totally    Indirect    Ceiling 

Luminaires  Suitable  for  the  Living  Room  Under  Various  Conditions 

Glass  shades   for  candle  fixtures  are  now  available  in  very  rich  and 

decorative  designs 

central  outlet  and  wall  brackets  on  separate  circuits.  Absence 
of  a  wall  switch  will  not  make  it  impossible  to  use  semi-indirect 
illumination,  for  small  switches  can  be  neatly  concealed  in  the 
canopy  fitting  and  operated  by  a  fine  cord.  The  living  room  re- 
quires the  maximum  number  of  convenience  outlets  for  at- 


taching  the  portable  lamps,  electric  fan,  phonograph  motor  and 
special  decorative  lighting  effects. 


Various  Means  for  Lighting  the  Living  Room  from  the  Sidewalls 

Dining  Room 

This  room  has  lighting  requirements  peculiar  to  itself;  rarely 


This   Night  View  of  the  Dining  Room  illustrates  the  Even  Illumination 
and  Absence  of   Shadows  Characteristic  of   Semi-indirect  Lighting 

is  it  used  as  anything  but  a  place  to  eat.  The  interest  therefore 
is  primarily  centered  on  the  table  and  this  interest  may  be 
increased  by  having  the  table  lighted  to  a  higher  intensity  then 
the  rest  of  the  room. 

113 


It  is  a  matter  of  personal  taste  which  way  the  dining  room 
shall  be  lighted,  whether  by  direct  or  indirect  methods.  The 
eld  style  dome,  while  often  crude  and  inartistic,  provided  a  most 
desirable  distribution  of  light.  The  table  was  the  brightest 
spot  in  the  room;,  yet  enough  light  was  transmitted  through 
the  glass  to  illuminate  the  corners  of  the  room,  preventing  too 
great  a  contrast.  There  are  several  requirements  which  must 
be  fulfilled  where  a  dome  is  employed.  It  must  be  hung  high 
enough  that  one  can  see  the  person  on  the  opposite  side  of 
the  table  and  yet  not  so  high  that  the  lamps  are  visible.  This 
will  place  the  bottom)  of  the  dome  about  56  inches  above  the 
floor.  A  dome  can  often  be  made  more  effective  by  using  a  small 
direct  lighting  reflector  inside  of  the  fabric  or  glass  to  send 
the  light  downward  and  conceal  the  lamp  from  view.  A  num- 
ber of  styles  of  domes  have  recently  appeared  on  the  market 
much  more  artistic  than  those  produced  in  the  past,  and  hence 
more  generally  applicable  to  the  home  where  harmony  is  sought. 
A  5O-watt  White  Mazda  lamp  will  give  the  desirable  intensity 
on  the  table  top  when  a  dome  is  employed  although  in  in- 
dividual instances,  higher  or  lower  values  are  considered  more 
pleasing. 

Some  people  prefer  the  room  more  uniformly  illuminated 
and  this  can  be  accomplished  by  the  use  of  the  semi-indirect 
system.  By  choosing  the  proper  density  of  glass,  a  suitable 
amount  of  light  will  be  transmitted,  the  table  receiving  more 
light  than  the  surroundings. 

For  this  system),  75-,  100-,  and  i5O-watt  Mazda  C  lamps  are 
applicable,  depending  on  personal  preferences  as  to  intensity 
and  on  the  color  of  surroundings.  It  is  often  possible  to  provide 
two  circuits  in  a  semi-indirect  luminaire,  one  giving  the  low 
illumination  for  setting  the  table. 

Luminaires  should  not  serve  as  sources  of  current  for  cook- 
ing devices.  A  convenience  outlet  should  be  installed  under  the 
edge  of  the  table,  and  this  in  turn,  attached  to  a  floor  plug.  A 
baseboard  convenience  outlet  near  the  buffet  or  serving  table 
permits  the  percolator,  toaster,  or  grill  to  be  used  without  the 
unsightly  collection  of  cords  dangling  from  overhead,  as  is  too 
commonly  the  case. 

Hall  or  Reception  Room 

Every  room  in  the  house  has  a  particular  meaning  and,  as 

114 


the  hall  is  the  first  one  entered,  a  feeling  of  hospitality  should 
prevail.  Lighting  can  be  of  great  assistance  in  attaining  this 
end. 

There  are  two  kinds  of  halls  just  as  there  are  two  varieties 


Some  Well  Designed  Dining  Room  Units.     It  is  of  interest  to  note  the 
tassel  at  the  bottom  of  the  semi-indirect  bowl.  This  conceals  half  of  an 
attachment    plug    for    use    with    cooking    devices.      The    wicker 
dome  carries  an   opalescent  reflector  indicated  by  dotted   lines 


of  porches.  One  is  merely  a  space  between  the  front 
door  and  the  rest  of  the  house,  the  other  is  of  the  reception  room 
type.  In  the  first  class  a  moderate  intensity  of  illumination 
suffices  and  a  25-watt  Mazda  lamp  in  a  suitable  diffusing  globe 
close  to  the  ceiling  will  furnish  enough  light  for  removing  one's 

"5 


wraps.  The  upstairs  hall  has  generally  the  same  requirements 
and  may  be  similarly  lighted. 

The  methods  of  lighting  the  living  room  are  quite  generally 
applicable  to  the  hall  of  the  reception  type.  Urn  shaped  en- 
closing globes  ?re  also  harmonious  with  many  interiors. 

The    control    for    hall    lighting    is    important.      Three-way 


These  Examples  are  Typical  of  the  Variety  of  Luminaires  that  are  Suitable 
for  the  Reception  or  Formal  Hall 

switches  are  most  desirable,  one  near  the  entrance  doorway  and 
the  other  at  a  convenient  point  in  the  second  floor  hall.  The 
slight  additional  expense  in  installing  these  is  more  than  offset 
by  the  security  and  comfort  gained. 

Bedroom 

The  general  arrangement  of  lighting  outlets  in  the  bedroom 
will   depend   upon    the    placement   of   the   furniture.      In   most 

116 


cases  it  is  desirable  to  provide  a  low1  intensity  of  general  illu- 
mination from  a  central  luminaire,  preferably  of  the  semi-indirect 
type,  although  frequently  silk-shaded  direct  luminaires  are 
suitable;  from  40  to  75  watts  are  desirable  in  this  unit.  It 
should  be  controlled  by  a  wall  switch  near  the  entrance  doorway 
to  avoid  stumbling  about  in  the  dark  in  search  of  the  key-socket. 


Dainty    Decorative    Luminaires     Suitable    for    the    Boudoir    are     Numerous. 

One  should  be  chosen  which  blends  with  the  color  treatment  of  the  room. 

Candle  fixtures  shaded  with  richly  colored  glass  give  good  illumination 

together  with  pleasing  color  effect 

A  higher  intensity  of  illumination  is  required  at  the  mirrors 
or  dressing  table  and  this  can  be  obtained  by  wall  brackets  or 
pendant  dresser  lights  harmonizing  with  the  central  unit  as  well 
as  the  rooml  decoration.  A  pendant  dresser  light  should  be 
placed  slightly  in  front  of  the  person  using  the  mirror.  A  con- 

117 


venience  outlet  near  the  bed  makes  it  possible  to  attach  a  heat- 
ing pad,  or  portable  lamp  for  reading  in  bed.  Another  near  the 
dresser  is  useful  for  attaching  an  electric  curling  iron,  heater 
or  fan. 

The  harmony  of  equipment  in  the  boudoir  is  very  important. 

Where  the  closet  is  in  such  a  position  that  it  does  not  re- 
ceive light  from  the  room  itself,  a  simple  type  of  receptacle 
should  be  provided  close  to  the  ceiling  with  a  low  wattage,  dif- 
fusing bulb  Mazda  lamp.  A  door  switch  for  such  a  position 
is  a  convenience  and  an  economy. 


The  Day  View  of  This  Bedroom  Gives  a  Good  Idea  of  How  Different 

Materials  May  be  Used  in  the  Lighting  Equipment  and  the  Results 

be    Harmonious.      The    fact    that    all    lamps    are    concealed 

from  view  is  indicative  of  comfortable  conditions 

Bathroom 

The  mirror  is  the  point  of  particular  interest  in  this  room 
and  the  lighting  must  be  planned  with  this  in  mind.'  The  face 
must  be  well  illuminated  before  it  can  be  viewed  in  the  mirror. 
Wall  luminaires,  one  on  each  side,  will  provide  satisfactory 
illumination  for  shaving.  The  I5~watt  diffusing  bulb  Mazda 
lamps  in  either  pendant  or  upright  shades  may  be  used.  A 
iamp  in  a  simple  diffusing  globe  close  to  the  ceiling  may  be 
used  for  general  illumination  where  additional  light  is  neces- 
sary. Care  should  be  taken  in  locating  the  lighting  outlets  in 

118 


the  bathroom  in  order  that  shadows  of  the  occupant  of  the  room 
will  not  be  cast  on  the  window.  Convenience  outlets  are  nec- 
essary for  the  electric  heater,  curling  iron,  hot  water  mug,  or 
vibrator. 


Neatness   and   Simplicity  are   Expressed   in    Such   Luminaires   as   These 
Applicable  to  the  Bathroom,  Closets  and  Passageways  Respectively. 


Parchment,    Silk,    and    Glass    are    Media    for    Directing    and    Diffusing    the 
Light.     Here   they  are  Applied  in   Neat   Dresser   Luminaires 

Porch 

In  order  that  the  home  may  invite  one's  friends  and  repel 
intruders,  the  porch  should  be  well  illuminated.  A  porch  often 
serves  merely  as  an  entrance,  but  may  act  as  an  outdoor  living 
room.  Of  course  in  these  two  cases  radically  different  lighting 
will  be  employed.  In  the  first  type,  only  a  small  amount  of 
illumination  is  required  for  safety  and  to  enable  one  to  see 
the  name  plate,  doorbell  or  button.  A  lo-watt  Mazda  lamp 


119 


will  burn  for  a  long  period  at  a  very  low  cost  and  serves  ex- 
cellently on  the  porch  in  a  weatherproof  enclosed  type 
globe,  lantern  fixture,  or  luminous  house  number.  An  outlet 
is  also  necessary  at  the  rear  porch  or  service  entrance.  In  the 
large  porch  or  sunroom,  much  novelty  can  be  introduced.  In- 
direct lum'inaires  of  metal  or  actual  wickerwork  lined  with 
cretonne  or  tinted  glassware  are  suitable  in  introducing  a  touch 
of  color  harmony.  Artificial  or  natural  flowers  or  vines  can 
be  effectively  applied.  Convenience  outlets  on  the  porch  for 
attaching  portable  lamps  or  other  devices  should  be  of  the 


The    Indirect    Light    Sources    in    This    Sunroom    Are    Inconspicuous    by 

Day  and  Add  to  the  Decoration  When  Lighted.  4O-watt  lamps  in  metal 

reflectors  are  concealed  by  the  artificial  flowiers  in  the  wire  baskets 

weatherproof  type  and  located  in  such  positions  that  they  will 

not  collect  moisture. 

Grounds 

While  the  subject  of  lighting  the  grounds  is  particularly  of 
interest  to  those  having  suburban  homes,  there  are  still  many 
parts  of  cities  where  the  street  lighting  may  be  supplemented 
by  a  lamp  at  the  entrance  of  the  driveway.  This  light  acts 
as  a  welcome  to  guests,  as  a  means  of  protection,  and  also  will 
contribute  to  the  appearance  of  the  property.  The  use  of  an 
ornamental  standard  that  matches  the  architectural  style  of  the 

120 


house,  with  an  opalescent  glass  globe  or  lantern  type  luminaire, 
is  good  practice.  A  5O-watt  [Mazda  lamp  in  this  will  enable 
the  driver  of  an  automobile  to  see  the  entrance  clearly. 

When  the  driveway  is  of  considerable  length,  it  becomes 
necessary  to  place  lights  at  least  at  sharp  curves  or  particularly 
dark  spots.  The  size  of  the  lamps  used  will  depend  upon  the 
surroundings  but  Mazda  lamps  ranging  from  25  to  75  watts 
should  fulfill  all  requirements.  It  is  necessary  that  these  lamps 
be  used  on  standards  that  will  raise  them  above  the  direct  line 
of  view  of  the  driver.  The  glassware  used  should  minimize 
glare  in  the  driver's  or  pedestrian's  eyes. 


The    Luminaire   for     the   Porch    Need   Not  be   of  a   Crude   Afterthought 
Nature,  but  can  be  Distinctive  at  a  Small  Additional  Cost 


Garage 

Electric  light  is  a  necessary  adjunct  to  the  garage  in  reduc- 
ing the  fire  hazard,  promoting  safety  and  making  adjustments 
and  repairs  in  a  satisfactory  manner.  General  illumination 
should  be  furnished  by  one  or  more  overhead  luminaires,  de- 
pending on  the  size  of  the  structure.  Bowl  enameled  Mazda  C 
lamps  in  steel  reflectors,  porcelain  enameled,  of  the  dome  type, 
are  desirable  for  this  service.  They  should  be  controlled  by  a 
wall  switch  near  the  entrance.  Several  convenience  outlets  are 
also  necessary  with  a  number  of  re-enforced  cords,  Mazda  mill 
type  lamps  and  wire  guards,  as  portable  lights.  In  working  on 
the  engine  and  transmission,  such  equipment  proves  of  value. 

121 


Wiring 

The  standards  for  proper  wiring  from  a  protective  basis  are 
established  by  local  underwriter's  codes  and  ordinances.  These 
must  be  adhered  to.  The  choice  between  different  systems  is 
governed  largely  by  economic  considerations  and  need  not  be 
discussed  here. 

Attention  should  be  directed  to  the  desirability  of  making 
the  initial  installation  complete.  A  given  amount  of  installation 
work  can  be  done  at  much  less  expense  when  doing  the  original 
work  than  at  a  later  date.  The  mistake  is  often  made  of  omit- 
ting convenience  outlets  and  wall  switches  in  order  to  keep 


Layout  of  Outlets  for  a  Typical  Small   House 


down  the  cost  of  wiring.  This  will  certainly  be  regretted  when 
one  begins  to  appreciate  that  some  of  the  real  advantages 
cf  electric  service  are  lost. 

The  statement  can  be  made  with  a  reasonable  degree  of  cer- 
tainty that  "one  cannot  have  too  many  outlets."  The  errors 
in  practice  are  all  in  the  other  direction.  A  satisfactory  layout 
ior  the  average  home  would  be  such  as  pictured  above. 

A  feature  which  should  be  incorporated  in  each  house  wired 
in  the  future  is  the  use  of  the  Elexit  or  the  standardized  lu- 
minaire  receptacle.  This  device  makes  it  possible  to  "hang  a 
fixture  like  a  picture"  and  one  can  change  bracket  or  ceiling 
iuminaires  at  will,  without  the  often  prohibitive  delay  and  ex- 


122 


pense  of  calling  in  an  electrician  to  make  any  connections. 
It  will  be  as  simple  to  move  a  fixture  from  one  room  to  an- 


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other  as  it  now  is  to  move  a  table  lamp.     A  person  living  in 
a  rented  home  need  not  be  content  with  the  lighting  that  hap- 


123 


pens  to  be  installed  but  can  use  his  owin  distinctive,  individual 
fixtures,  just  as  he  does  his  pictures,  draperies,  and  furniture. 

The  special  wiring  devices  which  add  materially  to  the  con- 
venience of  the  installation  are  almost  innumerable.  Among 
them  might  be  mentioned : 

T;he  switch  handle  or  small  indicator  on  a  pull  chain  sockei 
provided  wuth  luminous  material  which  glows  in  the  dark,  mak- 
ing it  possible  to  locate  the  control  readily. 

Switches  with  small  lamps  concealed  in  their  mechanism 
which  serve  to  indicate  that  the  attic  or  cellar  lights  are  burn- 
ing. Buzzing  devices  serve  the  same  purpose. 

Switches  which  can  be  attached  to  the  ceiling  or  concealed 
in  a  canopy  where  wall  switches  are  missing  and  it  is  not 
deemed  advisable  to  do  any  extensive  wiring. 

Three-way  switches  for  controlling  the  light  front  two  points. 

Two  or  more  circuit  switches  in  one  mechanism  to  produce 
various  degrees  of  lighting  by  pushing  or  turning  the  button  a 
certain  number  of  times. 

Switches  which  operate  automatically  when  a  closet  door  is 
opened  or  closed. 

Master  switches  for  lighting  the  whole  house  from  the 
owner's  bedside  in  case  of  emergency. 

Convenience  receptacles  which  can  be  installed  in  the  wall, 
baseboard,  floor,  or  under  a  table.  These  should  be  of  the 
standard  type  to  take  a  plug  with  ^-inch  parallel  blades  spaced 
J/2-inch  apart  so  that  all  plugs  are  interchangeable. 

Bell  ringing  transformers  which  do  away  with  maintaining 
batteries  for  this  purpose. 

Toy  transformers  which  can  be  used  to  provide  a  low  volt- 
age circuit  that  can  be  safely  used  in  the  nursery  for  children's 
electric  toys. 

Sockets  to  convert  candlesticks  so  that  they  will  serve  as 
electric  lamps. 

New  devices  of  this  nature  are  constantly  being  developed 
and  the  adaptability  of  electric  service  continually  broadening 
in  scope. 


124 


PART  VIII 
CHURCH  LIGHTING 

General  Requirements 

No  set  rules  can  be  laid  down  for  designing  church  lighting 
as  the  structures  vary  widely  in  type  and  the  artistic  effect  plays 
such  an  important  part.  In  other  words,  this  class  of  lighting 
cannot  be  standardized  as  that  for  the  industrial  plant,  office, 
or  store.  In  attempting  to  discuss  the  subject,  one  can  only 
outline  the  conditions  likely  to  be  encountered  and  schemes 
which  have  proven  satisfactory  in  service. 

The  illuminating  engineer  must  co-operate  with  the  architect 
and  bear  out  the  latter's  ideas  with  respect  to  the  lighting  effect 
to  be  attained,  and  specify  such  location  of  units,  types  of  fix- 
ture and  distributions  of  light  as  to  meet  these  criteria.  If  care 
is  taken  in  selecting  and  locating  the  lighting  fixtures,  these 
edifices  can  be  very  satisfactorily  lighted,  for  they  seldom  have 
brilliant  interior  finishes  to  cause  glaring  reflections;  the  ceilings 
usually  are  high,  thus  permitting  hanging  the  lamps  out  of 
ordinary  view. 

Observation  of  actual  installations  reveals  that,  if  our  homes 
were  as  poorly  lighted  as  many  of  our  churches,  it  would  soon 
have  a  serious  effect  on  our  vision.  As  We  are  in  the  church 
for  only  a  few  hours  every  week,  the  matter  is  not  given  suffi- 
cient thought. 

In  the  church,  in  contrast  to  the  theatre,  or  assembly  hall, 
the  lights  are  turned  on  the  entire  time  that  the  congregation 
is  present,  and  particular  attention  must  be  paid  to  the  arrange- 
ment of  lighting  units,  concealing  the  lamps  from  view  or  equip- 
ping them  with  diffusing  glassware. 

As  pointed  out,  the  lighting  units  should  be  in  architectural 
conformity  with  the  structure,  yet  utility  of  the  lighting  must 
be  given  consideration.  By  this  is  meant — first,  use  every  pre- 
caution to  prevent  eyestrain,  which  leads  to  drowsiness  and  at- 
<endant  discomfort;  second,  provide  enough  light  in  all  parts 
of  the  room  for  easy  reading.  Experience  has  shown  that,  if 
there  is  no  annoying  glare  or  bad  contrast,  an  intensity  of 
from  0.75  to  1.5  foot-candles  is  sufficient  for  reading  at  short 
intervals,  as  for  instances,  during  the  singing  of  a  hymn  or 
psalter  responses. 

It  is  impracticable  to  specify  the  wattage  necessary  to  obtain 
'he  desired  illumination  or  give  figures  on  the  utilization  con- 

125 


etants  for  the  different  systems  suggested,  due  to  the  wide  va- 
liation  in  character  of  surroundings. 

Methods  to  Avoid  in  Church  Lighting 

Huge  chandeliers,  unless  very  carefully  designed,  have  no 
architectural  significance,  and,  as  ordinarily  employed,  create 
severe  glare.  The  tendency  seems  to  be  to  hang  these  fixtures 
too  low  and  use  a  large  number  of  small  lamps.  With  this 
arrangement,  it  is  almost  impossible  to  avoid  glare,  and  many 
a  church  otherwise  pleasing  is  spoiled  by  such  lighting.  In  a 
number  of  instances,  fixtures  originally  intended  for  gas  jets 
or  low  powered  lamps  have  been  modified  to  accommodate  the 
brilliant  high  efficiency  modern  lamp  and  are  decidedly  objec- 
tionable. AVhere  such  fixtures  are  employed,  special  precau- 
tions must  be  taken  to  see  that  the  light  sources  are  of  low 
brilliancy. 

Studded  lights  around  the  capitals  of  the  pillars,  along  the 
beams  and  on  the  corbels  are  also  objectionable  for  it  is  almost 
impossible  to  avoid  annoying  images.  While  this  system  some- 
times brings  out  the  architectural  beauties  of  the  building,  it  is 
difficult  to  maintain,  and  each  burned  out  lamp  will  make  a 
break  in  the  continuity  and  spoil  the  effect  sought.  The  use 
of  this  system  will  occasionally  produce  freak  effects.  For  in- 
stance, a  row  of  small  lamps  around  the  capital  of  a  pillar  may 
give  the  appearance  of  an  open  space  and  leave  the  roof  and 
its  arches  without  visible  means  of  support.  The  efficiency  of 
this  system  is  low  and  renewal  cost  high. 

Bracket  units  at  the  front  of  the  church  and  decorative  light- 
ing around  the  pulpit  and  organ  are  particularly  objectionable, 
for  anyone  giving  attention  to  the  speaker  will  be  looking  to- 
ward these  bright  spots.  This  is  one  of  the  most  common 
causes  of  unsatisfactory  church  lighting. 

Feasible  Schemes  for  Lighting 

Churches  fall  in  two  distinct  groups — the  ritualistic  and 
the  evangelical.  In  the  former,  the  sanctuary  or  altar  is  the 
center  of  attraction  and  symbolically  demands  the  higher  in- 
tensity of  illumination.  In  the  evangelical  church,  the  maxi- 
mum illumination  should  be  provided  for  the  speaker,  pastor  or 
minister. 

The  very  structures  of  the  buildings  devoted  to  these  two 
groups  still  further  separate  their  lighting  requirements.  The 
ritualistic  church  is  generally  of  the  Gothic  type  of  architecture 

126 


with  the  nave  and  transept  forming  a  cross.  A  high  peaked 
i  oof  is  also  characteristic  of  this  form  of  structure  and  dark 
surroundings  are  likely  to  prevail.  In  the  evangelical  church, 
the  Basilica  type  of  structure  is  frequently  followed.  The 
ceiling  is  more  likely  to  be  light  in  color  and  also  flatter.  Even 
where  the  Gothic  style  of  architecture  is  employed,  it  is  usually 
modified  and  presents  less  of  a  lighting  problem. 

Ritualistic  Churches 

As  mentioned  before,  in  many  cases  the  ceiling  is  too  dark 
in  color  to  warrant  the  use  of  indirect  systems  of  lighting  and 
the  nave  and  transept  must  be  lighted  by  direct  overhead  units. 
The  following  systems  of  lighting  are  applicable  to  the  ritual- 
istic church  with  dark  surroundings;  those  buildings  with  light 
surroundings  can  be  well  lighted  by  the  methods  discussed  under 
evangelical  churches. 

A.  Direct    lighting   fixtures    consisting   of   clear   Mazda    C 
lamps  and  reflectors   enclosed  in   some   sort  of  an   ornamental 
housing.     This  housing  can  be  made  up  of  art  glass  and  wood, 
or  metal  work  in  the  form  of  a  lantern  to  enclose  one  or  more, 
equipments.    The  multiple  unit  fixture  offers  certain  advantages 
in  that  the  failure  of  one  unit  will  not  leave  an  entire  section 
in   shadow.     Mirrored  glass  reflectors  are  excellent  here,  but 
must  be  supplemented  by  a  few  low  wattage  lamps  inside  of 
the  fixture  to  illuminate  the  art  glass.    Translucent,  prismatic  or 
dense  opal  reflectors  are  also  effective  and  the  transmitted  light 
serves  the  purpose  of  the  small  lamps.     Such  fixtures  as  these 
can  be  relatively  large  suspended  from  the  peak  of  the  arch  or 
pmaller  in  size  dropped  from!  the  hammer-beams. 

B.  Diffusing  bulb   Mazda   lamps   in   simple   direct   lighting 
opalescent  glass  reflectors  can  be  suspended  from  the  hammer- 
beams   and   form   a   very   inexpensive   method   of   lighting.      If 
possible,  a  Gothic  type  of  decoration  should  be  secured.     As 
an  alternative  to  open  type  reflectors,  simple  types  of  enclosing 
globes  of  Gothic  design  can  be  used  in  the  same  position.    Opal- 
escent glass,  of  course,  gives  good  diffusion  but  the  whiteness 
of  the  glass  shows  up  in  contrast  with  the  background.     It  is 
desirable,  therefore,  to  employ  units  with  a  spray  of  light  brown 
or  similar  color.     The  slight  absorption  of  the  toning-  is  offset 
by  the  improved  appearance  of  the  installation. 

C.  Direct  lighting  angle  or  symmetric  reflectors,  with  clear 
Mazda  lamps,  can  be  placed  behind  the  hammer-beams,  sending 

127 


the  light  downward.  These  should  be  on  the  side  toward  the 
altar,  not  in  the  general  view  of  the  congregation,  and  if  the 
proper  type  of  reflector  is  chosen,  they  will  not  be  annoying  to 
the  speaker. 


A  Combination  of  Direct  and  Indirect  Illumination  is  Employed  in  This 

Gothic  Structure  of  Light  Gray  Stone.    Deep  bowl  mirrored  reflectors 

are  recessed  at  the  crossings  of  the  arches  of  the  main  and  side 

aisles.     These    are    the    300   and    2OO-watt    sizes    respectively 

D.  In  the  Gothic  structure,  with  light  surroundings,  a  com- 
bination of  direct  and  totally  indirect  lighting  is  often  applied 
with  excellent  results.  In  this  building  the  utilization  of  light 
from  an  indirect  system  would  be  of  a  very  low  order  due  to  the 
great  height,  in  comparison  with  the  w<idth.  Direct  lighting  re- 
flectors are  recessed  at  the  crossing  of  the  arches  and  the  indirect 
units  eliminate  severe  contrasts  in  brightness. 

128 


Evangelical  Churches 

Since  the  ceilings  of  many  of  these  buildings  are  light  in 
color  and  nearly  flat,  there  is  considerable  latitude  in  the  choice 


The    Smooth    Light    Colored    Ceiling   of   This   Auditorium    Lends    Itself 

to  the  Semi-indirect  System.     50O-watt  MAZDA   C  lamps  are  used 

in  the  four  large  central   units   and  eight  2OO-watt  units  of 

similar     design     are     placed     above     the     balcony 


Night  View  of  a  Church  with  Totally  Indirect  Fixtures  of  the  Luminous 

Bowl  Type.    General  illumination  is   furnished  by  500-watt   MAZDA   C 

lamps  in  inverted  mirrored  glass  reflectors  and  75  watt  MAZDA 

C  lamps,  in   smaller  angle  units   at  the   capitals 

129 


of  lighting  equipment.  In  contrast  to  the  pure  Gothic  struc- 
ture, all  three  systems  of  illumination — direct,  semi-indirect,  and 
totally  indirect — have  their  uses.  Frequently  the  architectural 
features  of  the  building  offer  certain  logical  places  for  the  at- 
tachment of  lighting  fixtures,  at  the  crossing  of  the  nave  and 
transept,  for  example,  or  at  symmetrical  points  along  the  main 
peak.  Balance  is  usually  desirable  in  the  location  of  outlets. 

Many  forms  of  direct  lighting  devices  suggest  themselves. 
They  should  generally  be  of  the  enclosed,  rather  than  the  open 
type,  as  the  likelihood  of  glare  is  then  diminished.  Decorated, 
opalescent  glass,  parchment,  and  painted  mica  are  among  the 
materials  which  can  be  effectively  used  for  this  purpose.  A 
very  wide  latitude  exists  in  the  choice  of  equipment.  The  funds 
available  for  fixtures  will  govern  this  factor.  As  an  example  of 
extreme  simplicity,  inexpensive  enclosing  units  with  clear  Mazda 
C  lamps  can  be  placed  at  the  apex  of  the  arches  separating  the 
side  aisles  from  the  main  aisle  in  the  modified  Gothic  structure. 
A  sufficient  spread  of  light  will  be  obtained  and  lighting  units 
will  be  well  out  of  view. 

Semi-indirect  units  symmetrically  spaced  are  applicable  to 
the  church  with  a  light  colored  ceiling  and  are  available  in  a 
wide  variety  of  decorations  which  will  harmonize  with  the  ar- 
chitectural design. 

Totally  indirect  illumination  can  be  accomplished  in  a  nurn- 
ter  of  ways.  Hanging  ceiling  fixtures  with  clear  Mazda  C 
lamps  in  mirrored  glass  reflectors  are  simple  to  install.  Smaller 
lamps  in  mirrored  glass  individual  or  trough  reflectors  can  be 
located  in  a  cornice,  or  groups  of  such  units  placed  in  recess 
at  the  tops  of  the  columns  or  capitals.  Wall  boxes  with 
suitably  designed  mirrored  glass  reflectors  have  also  been  em- 
ployed for  this  method  of  lighting.  Occassionally,  recessed 
windows  offer  logical  locations  for  such  equipment. 

Many  churches  are  provided  with  an  art  glass  ceiling  to  ad- 
mit natural  light.  Excellent  artificial  illumination  can  be  ac- 
complished by  properly  placing  direct  lighting  reflectors  and 
clear  Mazda  C  lamps  above  the  skylight.  Where  the  skylight 
is  limited  in  area  it  is  often  necessary  to  supplement  illumina- 
tion received  from  this  by  overhead  units  placed  between  it  and 
the  side  walls.  A  combination  of  semi-indirect  or  totally  in- 
direct illumination  and  the  diffused  direct  light  through  the 
sky  window  proves  effective. 

130 


For  balconies,  the  general  overhead  lighting  of  the  auditorium 
will  usually  take  care  of  the  balcony  itself.  Lighting  beneath 
the  balcony  can  be  accomplished  by  the  use  of  the  wall  type 
indirect  lighting  box  previously  mentioned,  close  ceiling  hemi- 
sphere or  flat  plates  attached  to  the  lower  side  of  the  balcony. 
The  glass  should  be  of  an  opalescent  character  giving  good  dif- 
fusion with  minimum  absorption. 

In  order  that  the  place  occupied  by  the  minister  or  speaker 
may  be  illumined  to  a  higher  degree  than  the  rest  of  the  church, 
it  is  desirable  to  have  some  means  of  projecting  light  on  the 
pulpit.  The  suspension  type  spot  lamp  with  concentrated  fila- 
ment Mazda  lamp  is  compact  and  can  be  hidden  from  view.  One 
of  these  units  located  above  the  speaker  will  produce  the  de- 
sired result.  It  should  be  focused  so  that  a  rather  widely  spread 
beam,  not  a  sharply  defined  spot,  is  obtained. 

Special  Lighting  Requirements 
Chancel 

On  account  of  the  desirability  of  concentrating  the  attention 
on  the  elaborate  ritual  held  in  the  sanctuary,  this  must  be  the 
most  brightly  lighted  portion  of  the  church,  and  yet  no  lights 
should  be  visible,  for  the  congregation  faces  in  that  direction. 
In  the  Gothic  structure  there  is.  usually  an  excellent  opportunity 
for  locating  the  units  behind  the  chancel  arch.  Steel  or  mir- 
rored glass,  angle  reflectors  simplify  the  problem  remarkably. 

The  sanctuary  should  have  plenty  of  light  to  bring  out  its 
decorative  value,  and  yet  the  altar  should  not  be  uniformly 
bright,  for  shadow  effects  are  then  lost  and  the  elaborately 
carved  portions  appear  flat  and  dull,  with  consequent  absence 
of  detail.  It  is  usually  better  to  light  the  altar  from  the  sides, 
simulating  the  daylight  values,  rather  than  from  the  top,  to 
avoid  any  deep  shadows  without  entirely  eliminating  them. 

The  lamps  should  be  so  arranged  that  the  choir  stalls  are 
well  illuminated,  and  it  is  often  desirable  to  have  the  units  on 
several  switches,  to  meet  the  demands  of  the  different  portions 
of  the  services. 

In  the  synagogue,  the  scroll  kept  in  a  cabinet  at  the  rear 
of  the  altar  should  be  illuminated  by  a  few  low  wattage  con- 
cealed lamps  placed  to  furnish  uniform  illumination.  A  switch 
turning  these  on  automatically  as  doors  are  opened  is  a  de- 
sirable accessory.  An  outlet  above  the  altar  or  a  low  wattage 
lamp  for  the  "Light  Everlasting"  and  convenience  outlets  for 


the    imitation    candlesticks    on    the    altar    are    also    necessary 
features. 

Choir  Loft 

In  the  evangelical  church,  this  occasionally  presents  a  prob- 
lem, often  being  located  at  the  front.  The  light  from  the  main 
auditorium  units  is  both  low  in  intensity  and  from  the  wrong 
direction. 

A  practice  is  often  followed  of  placing  a  few  brackets  on  the 
organ  and  shielding  the  lamps  with  some  sort  of  diffusing  shade. 
These  units  are  continually  in  the  vision  of  the  congregation  and 
are  extremely  annoying.  One  solution  is  to  place  the  lamps  in 
recessed  boxes  in  the  overhanging  portion  of  the  organ,  and 
diffuse  the  light  through  glass  plates.  If  the  organ  structure 
will  not  permit  of  this,  bowl  shaped  steel  reflectors  painted  on 
the  outside  to  harmonize  with  the  organ  finish  can  be  used  on 
brackets.  While  these  are  not  especially  decorative,  a  strong 
ight  is  provided  on  the  books  of  the  choir,  and,  as  the  re- 
flectors are  opaque,  the  eyes  of  the  congregation  are  protected. 
Reading  lamps  on  music  racks,  as  in  the  orchestra  pit  of  a 
theatre,  are  also  applicable  and  possess  many  advantages. 

A  local  lamp  is,  of  course,  provided  for  the  organist,  and  in 
many  instances  it  is  advisable  to  have  a  small  lamp  below 
the  keyboard  to  illuminate  the  pedals.  All  these  lamps  should 
be  separated  from  the  main  circuits  and  be  readily  controlled 
for  use  during  rehearsals. 

Windows 

Most  churches  have  at  least  one  elaborate  stained  art  glass 
memorial  window.  By  day  this  is  a  thing  of  beauty,  but  at 
tiight,  when  viewed  by  reflected  rather  than  transmitted  light, 
it  appears  as  a  dark,  dull  space.  In  most  cases  it  is  not  diffi- 
^ult  to  illuminate  the  window.  Weatherproof  type,  enameled 
steel,  angle  reflectors  with  clear  lamps  have  proved  of  use.  In 
most  cases  it  is  necessary  to  make  a  point  by  point  illumination 
calculation  to  determine  the  type  of  unit  and  its  location  for  the 
even  distribution  of  light,  and  this  can  often  be  supplemented 
by  some  slight  experimentation  to  determine  the  final  result. 

As  a  general  rule,  the  window  should  be  evenly  illuminated, 
and  it  is  bad  practice  to  have  the  light  source  visible  through 
the  glass.  Sometimes,  however,  there  is  a  point  in  the  design 
v/hich  logically  demands  a  higher  itensity  of  light,  as  for  ex- 

132 


ample,  the  sky  in  a  landscape  scene,  and  this  feature  must  be 
given  attention. 

For  large  windows  a  very  effective  method  is  to  project  from 
a  distance  a  beam  of  light  having  sufficient  spread  to  cover  the 
entire  window  area  with  a  uniform  intensity.  There  are  avail- 
able weatherproof  floodlighting  projectors  which  are  especially 
applicable  to  ihis  class  of  work.  They  can  be  mounted  on  a 
post  or  other  convenient  location,  from  25  to  300  feet  from  the 
window,  and  the  beam  trained  on  to  the  window  and  its  spread 
varied  as  necessary.  The  5OO-w'att  unit  is  sufficient  to  cover 
2O-foot  windows  with  the  unit  mounted  100  feet  away. 
Suggestions  Regarding  Wiring 

In  many  respects  the  demands  of  the  church  are  similar  to 
those  of  the  theatre  and  it  is  advisable  to  have  a  conveniently 
located  central  control.  Dimmers  are  an  especially  desirable 
feature,  both  on  the  main  and  chancel  circuits.  During  the  ser- 
mon, the  dimming  of  lights  produces  an  excellent  effect. 

An  experiment  with  colored  lighting  is  now  being  carried  on 
in  "St.  Mark's  Church  in  the  Bowurie,"  New  York  City.  Direct 
lighting  lantern  type  fixtures  are  used  to  produce  red,  amber, 
blue,  and  green  toned  illumination.  During  the  prayer  one  com- 
bination is  employed,  during  the  sermon  another,  at  the  offertory 
still  another.  The  psychological  effect  is  taken  into  considera- 
tion at  each  point,  blue  green  for  meditation,  red  and  amber 
for  stimulation,  and  so  on.  There  are  undoubtedly  wonderful 
possibilities  to  this,  and  the  future  will  see  great  developments. 
Such  manipulation  of  the  light  requires  a  number  of  circuits 
with  the  necessary  switching  and  dimming  controls. 

Standard  convenience  outlets  at  certain  points  about  the 
building  are  a  necessity.  In  some  churches  entertainments  are 
given  requiring  the  use  of  a  stereopticon.  A  stage  pocket  at 
the  rear  of  the  auditorium  with  sufficient  capacity  for  the  lan- 
tern is  a  feature  worthy  of  attention. 

The  moving  picture  is  becoming  a  factor  in  church  work  and 
.a  suitable  booth  for  the  machine  is  of  course  necessary. 

Convenience  outlets  throughout  the  auditorium  make  it  a 
simple  matter  to  attach  vacuum  cleaners. 

On  various  occasions  decorative  lighting  is  called  into  play 
as,  for  example,  at  Christmas  time  when  a  tree  might  be  illu- 
minated by  small  lamps.  A  receptacle  on  the  rostrum  or  stage 
is  necessary  for  such  occasions. 


Many  pastors  use  notes  and  a  reading  lamp  providing  a 
strong  localized  light  is  often  necessary. 

In  Catholic  churches  there  are  certain  services  and  part  of 
the  service  which  require  special  lighting  effects,  and  for  grand 
celebrations,  as  at  Easter  or  Christmas,  special  decorative  effects 
are  brought  into  play.  Adequate  capacity  in  convenience  out- 
lets must  be  provided  for  these  purposes. 

In  some  churches  candles  have  been  replaced  with  imita- 
tion candlesticks  and  all  frosted  MAZDA  candelabra  lamps.  In 
most  services,  however,  the  candle  has  a  symbolic  value  which 
should  be  retained. 

A  feature  often  overlooked  in  designing  a  lighting  system  is 
the  fact  that  reflectors  and  lamps  become  covered  with  dust 
which  very  materially  reduces  the  light  output  as  discussed  in 
another  section.  In  many  cases  complaints  of  poor  illumina- 
tion are  due  to  this  cause  alone.  In  the  church,  with  its  high 
ceiling,  fixtures  are  very  likely  to  be  most  inaccessible  and  the 
sexton  accordingly  is  hesitant  about  risking  his  safety  for  the 
sake  of  cleaning  the  units.  If  one  wishes  the  installation  to 
give  continuous  satisfaction,  he  should  keep  the  question,  "Will 
it  be  easy  to  clean  reflectors  and  replace  burned  out  lamps?" 
constantly  in  mind.  Equipment  should  be  located  so  that  it  is 
directly  accessible  or  lowering  devices  provided.  Automatic 
cutout  hangers  are  of  assistance  here  and  suitable  windlasses  for 
massive  fixtures  are  a  necessity. 


'34 


PART  IX 
LIGHTING  OF  PUBLIC  BUILDINGS 

Armories 

The  drill  shed  is,  of  course,  the  most  important  part  of  the 
armory  and  should  receive  the  most  attention.  As  a  general 
proposition  the  usual  form  is  a  large  open  space  with  an  arched 
roof.  The  size  of  those  investigated  varied  from  600  feet  by 
300  feet  (180,000  square  feet),  120  feet  high  to  76  by  92  (7,000 
square  feet),  38  feet  high.  The  roof  is  often  partly  glass  to 
admit  daylight  and  usually  the  iron  work  is  exposed. 

Many  drill  sheds  have  balconies  for  the  seating  of  spectators, 
necessitating  special  lighting  below  to  prevent  dense  shadows 
which  would  lesult  if  only  the  general  lighting  was  provided. 
The  floor  varies  considerably  depending  on  the  branch  of  serv- 
ice, cavalry  having  a  very  dark  brown  tanbark;  infantry,  light 
hard  wood.  Comparing  the  cavalry  drill  shed  having  a  floor  of 
low  reflecting  coefficient,  with  a  shed  having  an  ordinary  wooden 
floor,  approximately  twice  the  wattage  will  be  required  to  pro- 
duce corresponding  lighting  effects. 

On  account  of  the  simplicity  of  operation  and  maintenance, 
the  high  efficiency  of  light  production,  the  pleasing  color  of  light, 
and  the  steadiness  and  adaptability  to  reflectors  giving  any  de- 
sired distribution  of  light,  the  Mazda  C  lamp  has  become  prac- 
tically the  standard  illuminant  supplanting  all  other  forms  of 
equipment,  for  lighting  drill  sheds.  The  large  areas  permit  the 
use  of  high  candlepower  units  and  the  lofty  ceilings  give  hang- 
ing heights  such  that  lamps  are  always  well  out  of  the  ordinary 
angle  of  vision. 

The  uses  to  which  the  drill  hall  is  put  are  somewhat  varied. 
The  drilling  of  raw  recruits  takes  place  on  only  a  portion  of 
the  floor  and  does  not  require  the  entire  area  to  be  lighted; 
battalion  and  regimental  drills  and  reviews  necessitate  full  illu- 
mination for  ease  of  manoeuvres  and  inspection;  gun  drills  in 
the  coast  defense  and  artillery  sometimes  need  all  lights  out;  or 
the  armory  is  often  rented  to  charitable  organizations  and  the 
like  for  fairs  and  bazaars,  which  demiand  brilliant  lighting  as 
well  as  special  decorative  or  spectacular  effects.  In  any  event 
sufficient  light  must  be  provided  in  all  parts  of  the  room  to 
meet  the  most  exacting  conditions. 

In  most  cases  it  is  advisable  to  use  either  a  translucent  re- 


(lector  or  a  unit  which  permits  some  of  the  light  to  escape  above 
the  horizontal,  for  if  the  ceiling  is  totally  dark  the  room  seems 
unpleasant.  Occasionally,  however,  the  floor  is  light  enough 
to  reflect  sufficient  light  back  to  the  ceiling  even  if  opaque  bowl 
reflectors  are  employed. 

The  type  of  distribution  wiill  vary  with  conditions.     If  the 
side  walls  are  quite  dark  a  unit  giving  a  wide  curve  is  inadvis- 


Night  View  of  an  Infantry  Armory  (185  by  275  ft.,  40  ft.  to  Peak)  Green 

Side  Walls,  Green  Ceiling,  Light  Wood  Floor,  Lighted  by  28 

looo-watt  Clear  MAZDA  C  Lamps  in  Two-piece  Prismatic 

Enclosing    Units,    Steel    Cable    Suspension 

able  as  far  too  much  flux  wiill  be  wasted  by  wall  absorption. 
With  light  walls,  however,  the  diffuse  reflection  will  assist  in 
the  general  illumination  and  concentration  of  the  light  is  not 
as  necessary. 

In  compiling  the  material  for  this  section  a  total  of  thirty 
armories  were  investigated  as  to  equipment  and  spacing  of 
units,  condition  of  surroundings,  etc.  In  regard  to  the  reflecting 
equipment,  the  following  applies : 

Ten  were  provided  with  deep  bowl  dense  opal  direct  light- 
ing reflectors.  This  type  of  unit  is  low  in  first  cost  and  efficient 
in  directing  light  downward.  It  transmits  a  certain  percentage 
of  the  light  which  serves  to  illuminate  the  ceiling. 

Six  were  equipped  with  enclosing  globes  of  opalescent  glass 
with  an  external  porcelain  enameled  steel  reflector.  This  equip- 
ment is  comparatively  inexpensive,  gives  good  diffusion  and 
pleasing  light.  As  a  considerable  portion  of  the  light  is  in  a 
horizontal  direction  the  utilization  constant  is  rather  low. 

136 


Five  of  the  armories  employed  deep  oowl  large  mirrored 
glass  reflectors  which  are  very  efficient  in  redirecting  the  light, 
although  introducing  comparatively  little  diffusion.  They  are 
rather  high  in  first  cost. 

Four  buildings  utilized  deep  bowl  prismatic  glass  direct 
lighting  reflectors.  These  are  efficient,  of  moderate  price,  and' 
have  the  property  of  transmitting  a  small  proportion  of  the 
light  upward. 

On  account  of  the  high  hangings  employed,  some  sort  of 
a  lowering  device  should  be  provided.  Most  of  the  single  unit 
fixtures  weigh  so  little  that  a  simple  steel  cable  will  safely  sup- 
port them,  a  cut-out  hanger  with  lowering  rope  or  wire  simplifies 
this  phase  of  building  maintenance.  In  some  cases  the  cut-out 
is  omitted  and  the  cable  passed  through  a  pulley,  then  down 
the  sides  of  the  room,  the  current-carrying  wires  hanging  in 
loops. 


Night  View  of  a  Cavalry  Drill  Shed  (175  by  310  ft.,  70  ft.  to  Peak)  Cream 

Side  Walls,  Cream  Ceiling,  White  Sand,  Shavings  and  Loam  as  Floor, 

Lighted  by  31  75O-watt  Clear  MAZDA  C  Lamps  in  Deep  Bowl  Dense 

Opal    Direct    Lighting    Reflectors,    Steel    Cable    Suspension 

The  automatic  cut-out  hanger  is  a  desirable  feature  where 
lamps  are  hung  very  high  and  where  it  would  cost  considerable 
to  build  scaffolding  for  renewing  and  cleaning  lamps.  In  some 
armories,  a  walk  is  provided  around  in  the  roof  trusses  above 
the  units  from  which  they  can  be  maintained.  These  trusses 
are  usually  very  high  and  the  construction  of  the  walk  must  be 
carefully  considered  as  the  danger  element  is  large. 


Intensity  of  Illumination  Desirable 

From  general  considerations  the  cavalry  and  field  artillery 
armories  would  require  less  light  than  those  of  the  other  branch- 
es of  service,  as  they  are  not  likely  to  be  used  for  social  purposes. 
This  is  counteracted,  however,  by  the  fact  that  the  tanbark  or 
loam  floor  absorbs  a  great  deal  of  light  and  m^kes  the  place  ap- 
pear abnormally  dark. 

As  indicative  of  modern  practice  the  actual  power  consump- 
tion for  the  armories  with  wooden  floors  varies  from  .25  to  .55 
watt  per  square  foot,  the  average  figure  being  .37  watt  per 
square  foot.  The  illumination,  therefore,  varied  from  2  to  5 
foot-candles  with  the  average  in  the  neighborhood  of  3  foot-can- 
dles. Actual  tests  in  two  of  the  armories  investigated  showed 
approximately  2j^  foot-candles  of  illumination  quite  uniform  in 
character. 

In  the  armories  with  tanbark  floors,  the  actual  watts  per 
square  foot  varied  from  .23  to  .55  with  an  average  of  .34.  The 
average  generated  lumens  per  square  foot  were  6.2.  A  test  in 
one  of  these  showed  the  illumination  to  vary  between  2  and  4 
*oot-candles  with  an  average  of  3.25. 

GYMNASIUM 

General  Considerations — Main  Exercising  Floor 

This  is  usually  rectangular  in  shape  with  a  moderate  height  of 
ceiling.  The  arrangement  most  frequently  used  has  the  running 
track  as  a  balcony  6  to  8  ft.  wide  around  all  four  sides  of  the 
room.  In  the  center  of  the  main  floor  are  the  principal  pieces  of 
apparatus,  horses,  bucks,  jumping  standards,  and  parallel  bars, 
while  the  flying  rings  and  horizontal  bars  hang  from  the  main 
ceiling.  These  can  usually  be  pushed  aside  or  drawn  up  out  of 
the  way  for  basketball,  indoor  baseball  and  wrestling  matches, 
or  practice.  Below  the  balcony  are  found  the  exercisers  of  the 
various  types  and  racks  for  wands,  dumb-bells  and  Indian  clubs. 

The  center  part  of  the  space  requires  even  illumination  of  a 
moderate  intensity  w;ith  lamps  so  located  that  the  hanging  ap- 
paratus will  not  cause  dense  shadows.  Particular  attention 
should  be  paid  to  the  shielding  of  the  eye  from  the  lamp  fila- 
ment, for  one  is  forced  to  look  upward  a  great  deal  wlhen  playing 
basketball  and  often  faces  the  ceiling  in  ring  and  bar  work.  A 
blinding  effect  is  particularly  serious  at  such  times  and  may 
cause  a  bad  accident. 

138 


The  illumination  on  the  apparatus  attached  to  the  side  wall 
below  the  track  need  not  be  as  high  as  in  the  open  space,  yet  in 


Night   Photograph  of  a   Gymnasium  60  by   120  ft.,   Lighted  by  40O-watt 

Clear  MAZDA  C  Lamps  in  Semi-enclosing  Units  Consisting  of  a 

Diffusing     Glass     Dish     Suspended     Beneath     a     Large 

Porcelain  Enameled  Steel  Reflector 


Night   View   of   a   Tennis    Court    Showing    Lighting    Effects    Obtainable 

wdth   a   Combination  of  Semi-indirect  and  Totally   Indirect 

Lighting.     Eight  75o-watt  MAZDA  C  lamps  are  used 

many  cases  it  is  necessary  to  provide  a  few  outlets  here  with 
.small  lamps  properly  shaded  to  prevent  dense  shadows, 

i39 


The  general  discussion  on  choice  of  a  unit  given  under  armo- 
ries applies  here  also. 

In  investigating  the  lighting  of  gymnasiums,  data  were  col- 
lected on  the  equipment  utilized  in  42  typical  Y.  M.  C.  A.,  high 
school,  and  college  buildings.  It  was  unfortunate  that  nearly  50 
per  cent  of  those  examined  employed  old  style  equipment  con- 
sisting of  3,  4  or  12  lamp  cluster  bodies  with  flat  white  glass  or 


Night  View  of  a  Squash  Court  Lighted  by  Eight  4OO-watt  MAZDA  C  Lamps 
in  Opalescent  Semi-enclosing  Units.     The  wattage  con- 
sumption is  5.55  watts  per  square  foot  and  the 
intensity  is  approximately  10  foot-candles 

enamel  steel  reflectors.  These  were,  in  general,  placed  close  to 
the  ceiling  and  surrounded  by  wire  cages  or  guards.  This  type 
of  fixture  is  unsightly,  gives  a  very  poor  distribution  of  light  and 
is  inefficient,  as  light  from  one  lamp  must  pass  through  the  ad- 
jacent partially  blackened  bulbs.  These  flat  clusters  have  the 
particular  objection  that  they  expose  the  entire  filament. 

Of  the  twenty-two  gymnasiums  with  modern  equipment,  the 
following  types  were  employed ;  their  properties  are  discussed 
under  armories. 

Enameled  Steel,  Dome  Shape — 7 

Enameled  Steel,  Deep  Bowl  Shape — 1 

Mirrored  Glass,  Deep  Bowl  Shape — 4 

Prismatic  Glass,  Deep  Bowl  Shape — 2 

Opalescent  Glass,  Flat  Type — 2 

Opalescent  Enclosing  Globe — 3 

Opalescent  Enclosing  Globe  with  Enamel  Steel  Reflector— 2 

Opalescent  Glass  Semi-Indirect  Dish — I 

140 


In  these  twenty-two  buildings  the  minimum  watts  per  square 
foot  was  .42;  the  maximum  2.0;  the  average  .78.  The  average 
generated  lumens  per  square  foot  was  9.0.  As  most  of  the  equip- 
ment employed  is  of  an  efficient  character  and  side  walls  are 
generally  light  in  color  varying  from  white  to  natural  brick  and 
the  ceiling,  in  contrast  to  the  dark  ceiling  of  the  armory,  usually 
also  light,  a  fair  average  figure  for  the  intensity  of  illumination 
provided  is  between  4  and  5  foot-candles. 

Swimming  Pool 

This  room,  from  a  lighting  standpoint,  is  practically  a  modi- 
fied Ulbricht  sphere,  for  the  side  walls  and  ceiling  are  generally 
white  tile.  The  type  of  reflecting  device  employed  makes  but 
little  difference  in  the  illumination.  Care  should,  of  course,  be 
taken  to  insure  satisfactory  eye  protection. 


Swimming  Pool,  35  x  130  feet,  Lighted  by  7  200-watt  Diffusing  Bulb 
MAZDA   C  lamps  in  Dome   Enameled  Steel  Reflectors 

Running  Track 

Although  in  most  cases  this  extends  about  the  main  exercising 
room  and  the  general  illumination  is  sufficient  for  the  track, 
sometimes  a  long  track  is  installed  in  the  form  of  a  low  tunnel. 
Fttr  such  conditions,  angle  type  reflectors  pointing  in  the  direc- 
tion the  runner  is  proceeding  avoid  any  likelihood  of  glare  and 
direct  the  light  where  it  is  required. 


Miscellaneous  Exercising  Rooms 

These  comprise  the  wrestling,  boxing  and  fencing  rooms,  to- 
gether with  the  medical  director's  office.  Fencing  requires  a  rel- 
atively high  intensity  of  illumination  and  it  is  probable  that  one 
room  only  will  be  provided  for  all  these  sports.  In  such  cases 
the  lighting  layout  must  be  considered  from  the  standpoint  of 
fencing. 

Since  the  action  is  rapid,  it  is  essential  that  the  light  be  well 
diffused  and  of  high  intensity  in  order  that  all  movements  may  be 
readily  followed. 

The  finish  of  these  rooms  is  usually  light  in  color  with  smooth 
ceilings,  making  indirect  and  semi-indirect  systems  of  illumina- 
tion quite  feasible.  Approximately  I  wlatt  per  square  foot  of 
floor  area  with  MAZDA  C  lamps  proves  satisfactory  with  semi-in- 
direct lighting.  As  the  rooms  are  often  decorated  with  prizes, 
pennants,  etc.,  the  decorative  element  of  the  fixture  is  important. 

IrMthe  medical  director's  office,  the  ordinary  requirements  for 
office  lighting  are  experienced,  as  well  as  the  necessity  for  plenty 
of  light  in  all  parts  of  the  room  for  physical  examinations.    To- 
tally indirect  or  dense  glass  semi-indirect  units  are  suitable, 
Slhower  and  Locker  Rooms 

In  the  shower  room,  there  is  no  special  problem  in  regard  to 
lighting,  but  on  account  of  the  high  percentage  of  vapor  present 
in  the  air,  it  is  advisable  that  moisture-proof  electric  fittings  be 
employed. 

In  the  locker  rooms,  double  rows  of  lockers  with  aisles  be- 
tween in  most  cases  extend  to  the  ceiling.  The  athletes  dress  in 
these  aisles.  Mirrors  are  ordinarily  placed  at  the  ends  of  rows 
on  the  main  aisle.  Low  ceilings  of  light  color  make  practical  the 
use  of  low  candle-power,  all  frosted  lamps  without  reflectors, 
with  sockets  set  flush.  In  a  number  of  the  installations  exam- 
ined 25-watt  lamps  are  used  on  8  ft.  centers.  Larger  lamps 
with  suitable  reflectors  localized  near  the  mirrors  on  the  main 
aisle  are  essential.  A  6o-watt  lamp  with  bowtl-shaped  dense  opal 
reflectors  between  pairs  of  mirrors  proves  satisfactory. 

Lighting  of  Art  Galleries 

Proper  lighting  of  the  art  gallery  is  both  an  important  and 
interesting  subject.  The  buildings  themselves  represent  a  large 
expenditure,  are  more  or  less  monumental  in  character  and  dig- 
nity, and  consequently  require  artistic  and  harmonious  lighting. 
In  the  second  place,  priceless  collections  of  paintings  and  sculp- 

142 


ture  are  exhibited  here,  and  these  must  be  well  lighted  so  that 
the  public  may  view  and  study  them  in  comfort.  And  third,  in 
order  that  these  works  of  art  may  be  presented  so  that  the  de- 
tails will  stand  out  as  the  artist  conceived  them,  we  must  not 
only  have  ample  light,  but  direction  and  color  values  must  be 
carefully  considered. 
Paintings 

The  logical  arrangement  of  the  paintings  is  to  place  those  of 
a  dark  nature  at  the  top,  for,  with  predominant  light  from  above, 
the  higher  intensity  will  naturally  be  on  the  paintings  which  re- 
quire it.  We  see  by  reflected  light  and,  when  this  fact  is  consid- 


A  Night  View  of  a  Well  Known  Painting  Gallery  Illuminated  by  40-watt 

MAZDA  Lamps  in  a  Continuous  Rippled  Mirrored  Glass  Reflector. 

The  lamps  are  spaced  on   12-inch  centers  and  produce 

an  intensity  of  6  foot-candles  on  the  paintings 

ered,  it  at  once  becomes  apparent  that  by  this  arrangement  a 
more  uniform  and  attractive  gallery  is  the  result. 

The  background,  or  walls,  should  be  of  a  neutral  tone,  non- 
glossy  in  character  and  of  low  reflecting  power,  so  that  reflec- 
tions from  the  walls  are  eliminated  and  there  is  consequently 
nothing  to  distract  the  attention  from  the  exhibit.  The  neutral 
tone  is  of  special  importance  as  a  brilliantly  colored  background 
may  reflect  enough  light  to  mjodify  the  color  value  of  the  paint- 
ings quite  materially. 

There  are  two  general  methods  commonly  employed  in  the 
illumination  of  galleries — one,  where  the  lighting  is  accomplished 
from  the  sides,  and  the  other,  where  the  direction  of  light  simu- 
lates actual  daylight  conditions  and  comes  from  overhead.  What- 

143 


ever  system  is  used,  the  intensity  should  be  sufficient  to  illumi- 
nate the  dullest  piece  in  a  collection,  and  care  should  be  exer- 
cised to  see  that  specular  reflections  from  the  painted  and  glass 
surfaces  are  minimized.  The  reader  has  often  had  the  experience 
when  viewling  a  collection  of  being  annoyed  by  a  multiplicity  of 
reflections  which  distract  greatly  from  the  interest  of  the  exhibit. 


FIG.  2 

Section    of    a    Painting    Gallery,    Showing    How    an    Incorrectly    Placed 
Fixture   May   Result  in   Annoying   Specular   Reflections 

This  condition  is  most  frequently  encountered  where  the  side 
system  is  employed  as  evident  in  Fig.  2.  Here  the  paintings  are 
represented  as  illuminated  by  lamps  in  a  continuous  trough  re- 
flector, and  the  light  rays  are  indicated  by  the  broken  lines.  The 
collections  are  usually  viewed  from  the  area  between  A  and  B, 
and  eye  level  is  shown  by  the  dotted  line.  It  can  be  readily  seen 
from  the  sketch  that  any  slight  divergence  of  the  fixture  from  the 
correct  position  will  cause  the  light  rays  to  be  reflected  into  the 
area  from  which  the  paintings  are  viewed,  causing  annoying 
specular  reflection. 

Mirrored  glass  offers  certain  advantages  in  the  flexibility  of 
control  of  distribution,  but  plain  or  smooth  mirrored  surfaces 
should  never  be  employed  on  account  of  image  reflections.  For 
temporary  installations,  white  paint  enamel  gives  excellent  re- 
sults from  the  standpoint  of  reflective  properties  and  diffusion, 
but  for  permanent  installations  is  quite  out  of  the  question,  as  it 
turns  brown  from  the  heat  of  the  lamp,  blisters  and  peels,  as  well 
as  accumulates  dust,  thus  having  its  reflecting  power  considera- 
Lly  lowered.  For  ordinary  conditions,  from  40  to  60  watts  per 
running  foot  of  wall  space  will  provide  an  intensity  of  approxi- 
mately 6  foot-candles  on  the  picture. 

It  is  certainly  desirable,  when  the  construction  of  the  build- 
ing  permits,  to  utilize;  the  skylight  as  a  method  of  illuminating 

-        -    .144 


paintings,  for  not  only  can  a  better  lighting-  effect  be  obtained, 
but  the  appearance  of  the  room  without  fixtures  is  much  more 
attractive. 

In  a  system  of  this  type,  the  hanging  height  of  the  units  above 
the  skylight  will  depend  upon  the  wattage  of  the  lamps  used,  and 
upon  the  glass  in  the  skylight.  The  lamps  and  reflectors  should 
be  so  arranged  that  the  glass  presents  a  uniform  appearance 
trom  the  room  below,  and  the  glass  itself  should  be  of  such  a 
nature  that  the  lighting  source  cannot  be  discerned  through  the 
glass. 

In  some  instances  angle  units  can  be  so  suspended  as  to  di- 
rect the  light  on  the  opposite  wall  and  are  generally  preferable 
on  account  of  their  higher  vertical  components  to  reflectors  giv- 
ing a  symmetrical  distribution  of  light.  Projector  units  have  also 
been  successfully  applied  to  this  service,  their  advantages  being 
accurate  control  of  light  distribution  and  compactness.  To  avoid 
spotted  appearance  of  the  glass  it  is  sometimes  necessary  to  em- 
ploy opaque  shields  to  obstruct  the  direct  light.  With  an  instal- 
lation of  this  type  it  is  advisable  to  employ  a  glass  which,  while 
concealing  the  location  of  the  lamps,  does  not  materially  affect 
the  distribution  of  light  by  introducing  a  great  amount  of  dif- 
fusion. 

Another  factor  which  requires  consideration  when  the  gallery 
is  equipped  with  a  skylight,  is  the  continually  changing  quality 
of  daylight  so  that  some  system  or  method  of  modifying  the  in- 
tensity should  be  provided  for.  This  may  be  effectively  accom- 
plished by  installing  a  system  of  adjustable  louvres  between  the 
sub-skylight  and  the  main  skylight.  The  louvres  may  be  of  thin 
metal  painted  white,  or  may  be  of  cloth  on  wooden  frames,  and 
in  either  case  they  should  be  controlled  either  pneumatically  or 
electrically  from  the  room  below.  Thus,  when  the  sun  is  in  such 
a  direction  as  to  light  one  wall  to  a  higher  intensity  than  the  op- 
posite, the  attendant  may  adjust  the  louvres  until  more  uniform 
illumination  is  obtained. 

A  much  simpler  method  is  to  provide  a  white  diffusing  curtain 
between  the  two  skylights  which  can  be  drawn  across  the  sky- 
light when  the  intensity  is  too  high.  This  system  is,  of  course, 
less  expensive,  but  is  by  no  means  so  satisfactory  or  flexible  as 
the  former. 

The  question  of  proper  color  quality  of  artificial  light  for  an 
art  gallery  can  be  viewed  from  many  angles.  All  of  us  know 

MS 


that  a  distortion  of  hue  results  when  lights  of  different  spectral 
characteristics  fall  on  colored  objects. 

From  a  theoretical  standpoint  in  displaying  a  painting,  it 
seems  most  logical  to  attempt  to  reproduce  conditions  under 
which  it  was  conceived.  A  picture  painted  by  daylight  obviously 
transfers  the  artist's  conception  best  under  natural  light,  while 
those  painted  in  artificial  light  should  have  similar  treatment. 

In  an  art  gallery,  however,  we  find  all  types  in  the  same 
group,  and  even  the  position  of  individual  works  may  be  changed 
fromi  time  to  time.  It  is  scarcely  expedient  to  be  constantly 
shifting  the  lighting. 

It  is  probable  that  the  majority  of  pictures  were  produced 
tinder  daylight  conditions  and  the  MAZDA  Daylight  lamp  is  a  suit- 
able light  source  for  the  art  gallery.  It  is  a  compromise  between 
unmodified  artificial  light  and  average  daylight,  sufficiently  effi- 
cient to  warrant  its  use.  When  lamps  of  this  character  are  used, 
the  transition  at  nightfall  is  much  less  noticeable. 

There  is  another  phase  of  the  question  which  is  not  generally 
applicable  to  the  large  gallery  and  is  possibly  open  to  objections 
on  the  part  of  the  true  connoiseur,  that  is,  special  lighting  by 
tinted  lamps  of  individual  pictures.  Many  paintings  appear  to 
better  advantage  when  so  lighted.  Certain  colors  or  tones  may 
be  accentuated  or  subdued  with  skillful  treatment.  Again,  each 
picture  may  be  illuminated  .by  light  with  a  certain  predominating 
direction,  coincident  with  the  general  direction  of  light  in  the  pic- 
ture, thus  heightening  the  contrast.  This  field  presents  many 
varied  and  interesting  problems  and,  in  general,  needs  specialized 
study  of  each  individual  work. 

Statuary 

The  sculptor  may  choose  the  most  perfect  piece  of  marble 
and  model  it  into  a  sublime  work  of  art,  a  perfect  reproduction  of 
his  inspired  vision,  yet  a  careless  arrangement  of  the  work  with 
reference  to  predominent  light  may  cause  unseemly  distortions 
and  a  shattering  of  the  expressed  ideals. 

The  beauty  of  statuary  lies  in  the  relation  of  high-lights  and 
shadows.  The  desirable  density,  sharpness,  and  quantity  of 
shadow's,  depend  upon  the  emotion  to  be  depicted.  Tragedy  de- 
mands sharp  contrast  and  bold  shadows,  as  exemplified  in  the 
Laocoon  group.  On  the  other  hand,  a  piece  of  work  similar  to 
Aphrodite,  portraying  soft,  subtle  modelling,  and  a  face  of  ra- 
diant pleasure,  needs  a  softer  light  to  bring  out  the  effect  of  the 

146 


more  quiet  emotion.  Shadows  are  troublesome  in  sculpture  only 
when  they  tend  to  produce  false  impressions. 

Under  artificial  light,  the  degree  of  shadows  produced  de- 
pends upon  the  type  of  unit  used.  If  a  direct  lighting  system  is 
employed,  the  sharpest  of  shadows  are  produced  with  little  dif- 
fusion, except  that  reflected  from  surrounding  surfaces,  such  as 
walls  and  floors.  With  a  totally  indirect  system,  of  course,  a 
minimum  of  shadows  is  obtained  and  this  lighting  is  scarcely  of 
service.  With  semi-indirect  units,  however,  we  have  a  particu- 
larly fortunate  condition.  The  proportion  of  direct  to  diffuse  or 
reflected  light  is  dependent  on  the  density  of  the  glass  of  the 
bowl  or,  with  a  given  density  of  glass,  these  factors  can  be  varied 
by  tinting  and  toning  the  ceiling,  increasing  its  absorption.  En- 
closing or  semi-enclosing  diffusing  units  having  similar  proper- 
ties to  semi-indirect  units  are  also  useful  in  producing  a  suitable 
combination  of  direct  and  diffuse  light. 

A  systematic  arrangement  of  either  of  these  two  latter  types 
of  units,  providing  an  intensity  of  from  4  to  6  foot-candles,  gives 
good  results.  Since  a  greater  amount  of  direct  light  is  usually 
produced  immediately  beneath  the  outlet,  it  is  quite  logical  to 
locate  in  such  positions  objects  requiring  well  defined  shadows 
and  those  of  "softer"  lines  in  the  more  diffusely  lighted  areas. 
Thus,  artificial  light,  on  account  of  the  possibility  of  readily 
changing  the  intensity,  color  and  direction,  is  one  of  our  best 
mediums  of  artistic  treatment.  Crude,  stagey  effects  should  be 
avoided  and  one  must  realize  that,  while  lighting  cannot  make 
art,  it  can  certainly  mar  it. 

Lighting  of  Museums 

Our  museums  contain  priceless  collections  of  natural,  scien 
tine,  and  literary  curiosities,  conveniently  exhibited  where  the 
public  may  view  and  study  them  at  leisure.  It  is  important  that 
the  specimens  be  arranged  and  displayed  to  their  best  advantage, 
and  this  cannot  be  accomplished  unless  the  exhibit  is  properly 
illuminated  to  facilitate  careful  study. 

There  must  obviously  be  good  general  lighting,  special  light- 
ing of  a  high  intensity  for  small  objects  in  show  cases,  and  more 
or  less  of  stage  lighting  effects  where  a  group  is  presented  in  its 
natural  setting. 

Glaring  light  sources  and  reflected  images  must  be  avoided, 
for  there  is  no  one  factor  which  tends  to  reduce  the  effectiveness 
of  a  museum  more  than  annoying  reflections  in  the  glass  surfaces 

147 


of  the  cases.  A  well  diffused,  general  lighting  is  required,  of  an 
intensity  of  6  to  8  foot-candles,  so  arranged  that  it  will  not  cause 
objectionable  shadows  on  the  exhibits.  The  indirect  systems  or 
diffusing  direct  lighting  units  of  neat  simple  lines  meet  these  de- 
mands. The  fixture  itself  should  be  dignified  and  in  conformity 
with  the  architecture  of  the  building.  In  the  foyer  and  similar 
places,  massive  ornamental  standards  or  multiple  unit  fixtures 
are  frequently  necessary  for  their  decorative  value. 

The  lighting  of  exhibit  cases  is  obviously  an  important  fea- 
ture. In  general,  they  may  be  divided  into  two  distinct  groups 
—those  constructed  entirely  of  glass  and  readily  illuminated  by 
the  general  system,  and  those  which  have  an  opaque  top,  or  are 
of  such  a  nature  as  to  require  local  illumination.  The  wall  cases 
usually  have  a  cornice  at  the  top  behind  which  lighting  equip- 
ment may  be  readily  installed  in  an  inconspicuous  manner.  As 
inbst  of  the  cases  are  air-tight  in  order  that  they  may  be  dust- 
proof,  it  is  important  that  low  wattage  lamps  be  employed  to 
prevent  excessive  heating.  Small  mirrored  glass  or  metal  in- 
dividual reflectors  or  continuous  trough  equipment  can  be  util- 
ized. 

The  most  interesting  phase  of  museum  lighting  is  that  of 
providing  special  effects  for  cases  or  alcoves  containing  objects 
in  their  natural  surroundings.  The  principles  of  stage  lighting 
have  been  applied  to  the  show  window  with  excellent  results. 
They  are  especially  applicable  here.  The  method  of  handling 
individual  exhibits  will  depend  on  the  construction  of  the  case 
and  the  ingenuity  of  the  designer. 

The  laboratory  and  workshops  of  the  museums,  where  fig- 
ures of  the  groups  are  cast  or  modelled  specimens  mounted, 
magnified  copies  of  objects  made  in  glass  and  wax,  and  models 
of  all  sorts  repaired,  offer  no  problem  distinct  from  those  of  the 
ordinary  industrial  plant,  with  similar  demands  on  vision.  A 
high  intensity  of  general  illumination  with  efficient  direct  light- 
ing units,  such  as  RLM  Standard  dome  reflectors  and  bowl  enam- 
eled MAZDA  C  lamps,  will  permit  accurate  work  amid  pleasing 
surroundings.  Convenience  outlets  to  which  suitably  shielded 
local  lamps  can  be  attached  are  necessary  along  the  benches  in 
order  that  the  very  high  intensity  necessary,  when  working  on 
minute  objects,  can  be  available. 

Lighting  of  Libraries 

The  use  of  a  library  reflects  to  a  greater  or  less  degree  the 

148 


intellectual  and  artistic  standing  of  the  community,  and  there  is, 
perhaps,  no  better  way  to  invite  patronage  than  by  making  the 
interior  attractive  and  comfortable.  Even  though  the  building  is 
beautifully  designed  and  well  provided  with  books,  unless  its 
lighting  is  suitable  and  adequate,  it  is  not  a  thoroughly  effective 
institution.  The  primlary  function  of  the  lighting  installation  is 
to  enable  printed  matter  to  be  read  with  ease,  but  in  addition  it 
offers  an  opportunity  for  accentuating  the  architectural  design 
and  beauty  of  the  building. 

Libraries  may  be  divided  into  two  quite  distinct  classes — one, 
the  monumental  building  of  the  large  city  where  the  rooms  are 
spacious,  ceilings  high,  corridors  handsomely  finished  in  marble, 
and  where  the  element  of  decoration  plays  a  large  part.  Reading 
rooms  in  this  class  of  building  are  generally  separate  from  the 
stack  room.  The  other  is  represented  by  the  branch,  public 
school,  or  town  library,  unpretentious  in  nature,  where  the  books 
are  stored  in  cases  around  the  room.  Here  the  decorative  fea- 
ture is  secondary  and  utility  of  light  plays  a  more  important  part. 

It  is  quite  common  practice  to  install  decorative  fixtures  in 
the  high  ceiling  reading  room,  of  the  first  class  of  buildings.  These 
supply  a  moderate  intensity  of  general  illumination,  necessary 
for  supervision  and  to  prevent  severe  contrasis  of  brightness,  but 
are  seldom  designed  to  supply  enough  light  for  continued  read- 
ing. All  too  frequently,  the  decorative  value  is  apparently  the 
only  element  of  design  given  sufficient  weight,  and  examples  are 
well  known  of  glaring  and  hence  ineffective  installations.  Un- 
shaded lamps  are  studded  in  huge  clusters,  sometimes  unfortu- 
nately in  the  field  of  view'.  It  is  quite  out  of  the  question  to  lay 
down  specific  rules  on  this  phase  of  lighting,  for  individual  taste 
varies,  and  earnest  co-operation  between  the  architect,  fixture 
specialist,  and  illuminating  engineer  is  advisable. 

In  addition  to  the  general  illumination  of  from  2  to  4  foot- 
candles,  local  lighting  should  be  supplied  on  the  tables.  TJhese 
lamps  should  be  very  carefully  chosen,  so  placed,  and  of  such  a 
character  that  direct  or  reflected  glare  is  minimized.  Many 
standard  types  in  wide  use  are  most  inappropriate  and  produc- 
tive of  eye  fatigue.  An  even  distribution  of  light  on  the  table  top 
of  an  intensity  of  6  to  8  foot-candles,  is  suitable,  although  higher 
intensities  are  sometimes  necessary  where  faded  manuscripts  or 
books  with  very  fine  type  are  likely  to  be  used. 

In  many  respects  proper  table  lighting  is  an  economy,  pro 

149 


ducing  a  high  intensity  over  the  working  area  while  a  lower  in- 
tensity is  sufficient  in  the  rest  of  the  room.  This  is  particularly 
important  in  the  library  at  night  where  but  few  readers  are  like- 
ly to  be  present.  Each  reader  will  then  control  his  own  local 
illumination;  the  attention  will  be  concentrated  upon  the  work. 

As  mentioned,  in  the  reading  room  of  the  second  class  of 
luildings  are  located  the  book  stacks,  and  general  lighting  with 
the  indirect  systems  is  the  most  logical  method  of  meeting  the 
requirements.  With  the  present-day  high  efficiency  lamps,  it  is 
perfectly  advisable  to  supply  from  6  to  8  foot-candles  throughout 
the  room.  This  eliminates  the  necessity  and  bother  of  local  or 
table  lights.  The  diffuse  character  of  the  illumination  thus  pro- 
duced gives  excellent  lighting  on  the  vertical  surfaces  of  the 
stacks. 

Tfae  catalog  room  of  the  city  library  is  generally  lighted  by 
massive  ornamental  fixtures  and  the  remarks  relative  to  the 
reading  room  apply  to  this  part  of  the  building.  Simple  brack- 
ets, attached  to  the  riling  cabinets,  carrying  relatively  low  watt- 
age lamps  in  deep  bowl  or  angle  reflectors  increase  the  intensity 
of  illumination  in  that  region  to  6  or  8  foot-candles. 

The  periodical  rooms  and  special  reading  rooms  are  similar  in 
nature  to  the  small  library,  and  the  type  of  lighting  suggested 
for  use  there  fits  these  conditions. 

In  the  stack  room,  the  titles  and  numbers  on  the  books  must 
be  readily  discernible,  and  an  average  intensity  of  from  2  to  4 
foot-candles  is  desirable.  Twenty-five  or  5O-wlatt  MAZDA  lamps 
with  deep  bowl  opalescent  glass  reflectors,  attached  to  a  line  of 
overhead  conduit  over  the  aisles,  on  6  to  10  foot  centers,  will 
fulfill  the  demand.  Where  the  aisles  are  of  considerable  length, 
three-way  switches  at  both  ends  are  an  economy  in  enabling  the 
attendant  to  switch  on  the  required  lights  and  to  extinguish  them 
after  the  desired  book  has  been  obtained. 
Lighting  of  Municipal,  County,  and  State  Buildings 

The  larger  portion  of  these  structures  is  devoted  to  private 
and  clerical  offices,  the  illumination  of  which  has  been  thorough- 
ly discussed.  Entrances,  corridors,  and  reception  rooms  are  sim- 
ilar in  demand  to  those  in  the  museum,  and,  where  inscriptions 
and  mural  paintings  prevail,  care  should  be  taken  to  see  that  the 
type  of  unit  chosen  for  lighting  permits  these  to  be  seen  in  a 
clear  and  effective  manner. 

Committee  and  jury  rooms  have  the  same  general  requirements 
as  the  office,  although  a  lower  intensity  (3  to  5  foot-candles)  is 

150 


sufficient.  In  many  instances,  however,  these  rooms  are  finished 
in  dark  wood,  which  makes  the  lighting  problem  considerably 
more  complex.  Bracket  units  with  unshielded  lamps  must  be 
avoided,  and  diffusing  enclosing  globes,  well  out  of  the  angle  of 
view,  offer  probably  the  best  solution.  The  character  and  design 
of  the  supporting  fixture  will  depend  on  the  elaborateness  of  the 
decoration. 

Figuratively  speaking,  light  and  justice  are  always  associated, 
and  yet  an  investigation  of  the  lighting  in  our  court  and  assem- 
bly rooms  shows  them  to  be,  in  many  instances,  dark  and  dingy. 
When  necessity  arises  for  proving  physical  facts  by  visible  evi- 
dence, it  is  often  difficult  to  observe  the  details  of  the  exhibit. 
During  a  court  trial,  it  is  certainly  desirable  that  the  judge  and 
jury  should  see  the  witness  with  the  utmost  distinctness  as  testi- 
mony is  being  given,  and  it  is  evident  that  proper  lighting  is 
essential. 

Many  of  our  court  rooms  are  still  illuminated  by  open  burner 
gas  jets,  or  by  old  gas  fixtures  which  have  been  slightly  altered 
to  accommodate  such  electric  lamps  as  would  go  inside  the  globe, 
without  any  forethought  from  the  standpoint  of  intensity,  distri- 
bution, or  diffusion. 

The  general  lighting  requirements  are  similar  to  those  of  an 
auditorium,  and  lighting  units  even  though  of  a  decorative  na- 
ture, should  be  suspended  well  out  of  the  line  of  vision.  Wall 
brackets  at  the  front  of  the  room  are  especially  objectionable,  as 
they  are  continuously  in  the  field  of  view,  and  one's  attention  is 
naturally  directed  toward  the  judge  and  witness. 

While  stage  effects  are  not  in  especially  good  taste,  there  is 
no  reason  why  advantage  should  not  be  taken  of  some  of  the 
principles  utilized  so  effectively  on  the  stage.  If  the  director 
desires  to  focus  the  attention  of  the  audience  on  a  particular  part 
of  the  scene  or  on  one  actor,  he  illuminates  this  area  to  a  higher 
intensity  by  the  use  of  a  spot  lamp  of  some  sort.  If  the  con- 
struction of  the  building  is  such  as  to  permit  a  suspension  type 
spot  lamp  to  be  concealed  from  view,  it  would  seem  fairly  logical 
to  direct  the  light  from  this  on  the  witness  stand.  A  sharply  de- 
fined spot  would  not  be  desirable,  but  on  the  other  hand,  one 
which  shaded  off  gradually  would  produce  the  desired  effect 
without  being  noticed  by  the  casual  observer. 

There  are  many  cases  which  come  to  trial  where  the  verdict 
depends  on  a  close  examination  of  the  evidence,  as  in  the  case  of 

151 


torgery,  or  an  erasure  in  a  document.  Much  time  may  be  lost  if 
the  case  has  to  be  adjourned  to  an  adequately  lighted  room  in 
order  to  view  the  exhibit.  If  convenience  outlets  are  provided  to 
which  local  lamps  giving  a  high  intensity  of  illumination  can  be 
attached,  this  work  can  be  carried  on  without  loss  of  time.  The 
accurate  type  of  color  identification  unit,  providing  illumination 
of  a  high  intensity  over  a  small  area  of  a  true  daylight  value, 
should  be  useful. 
Lighting  of  Banks 

The  lighting  system  in  the  bank  should  be  such  as  to  impress 


A   Well    Lighted    Bank    Using   30G-watt    MAZDA    Lamps    in    Semi-indirect 

Bowls    on    Centers    18   by   32    feet.      The    fixtures    are    simple    yet 

dignified  and  provide  a  uniform  intensity  of  5   foot-candles 

throughout   the   main   banking   space 

the  patrons  with  the  dignity  of  the  institution,  and  yet  eliminate 
any  idea  that  the  building  is  simply  a  cold  storage  place  for  cur- 
rency, by  making  the  interior  comfortable  and  inviting.  A  high 
intensity  of  illumination  will  eliminate  eye  fatigue  and  thus  pre- 
vent opportunities  for  errors,  and  will  increase  the  speed  of  the 
clerical  force.  It  is  an  asset  in  advertising  the  bank,  and  many 
deem  it  advisable  to  leave  the  light  burning  at  night  for  this 
purpose,  as  well  as  for  protective  value. 

With  the  high  efficiency  of  the  present-day  illuminants  the 
old  form  of  local  or  drop  lighting  is  gradually  being  eliminated, 
end  the  multiplicity  of  unsightly  cords  and"  tin  shades,  which 
formerly  occupied  the  space  behind  the  cages,  is  becoming  a 
thing  of  the  past.  The  main  banking  space  should  be  equipped 
with  general  lighting  of  an  intensity  of  from  4  to  5  foot-candles. 
Almost  any  form  of  fixture  which  harmonizes  with  the  architec- 

152 


tural  features  might  be  used,  providing  it  fulfills  the  general  re- 
quirements as  to  distribution  and  diffusion.  If  the  general  light- 
ing is  not  sufficient,  patrons'  'desks  should  be  equipped  with  local 
units  producing  an  intensity  of  from  8  to  10  foot-candles.  The 
general  type  of  these  units  should  be  similar  to  those  recom- 
mended for  reading  in  the  library,  and  they  should  be  so  located 
as  to  prevent  direct  and  reflected  glare.  The  exterior  of  the  fix- 
ture obviously  should  harmonize  with  the  other  metal  work. 

The  general  lighting  system  is  often  supplemented  by  cage 
grill  fixtures  to  raise  the  intensity  at  the  various  wickets  to  a 


A  Night  View  Showing  a  Typical  Cage  Grill  Fixture  Employing  25-watt 
MAZDA    Lamps    Spaced    about    14    Inches    Apart 

value  of  approximately  10  foot-candles.  The  distribution  of  light 
should  be  such  as  to  prevent  glares  and  a  diffusing  glass  plate 
over  the  opening  should  be  used  to  prevent  annoying  reflections 
of  lamp  filaments. 

The  vaults  are  used  primarily  for  the  storage  of  valuable 
documents,  and  little  actual  work  is  carried  on  here.  A  lower 
intensity  (3  to  4  foot-candles)  suffices.  In  most  instances  it  is 
inadvisable  to  pierce  the  armor  plate  of  the  safe  to  furnish  elec- 
tric current  for  lighting  purposes.  A  convenient  arrangement  to 
overcome  this  difficulty  is  to  locate  one  receptacle  outside  of  the 
vault  connected  to  the  power  supply,  and  another  inside  of  the 
vault  feeding  !he  lighting  circuit.  When  the  steel  door  is  opened, 
a  flexible  cable  with  a  plug  at  each  end  connects  the  two  recep- 
tacles. A  circuit  breaker  installed  on  the  line  is  som'etimes  used 
as  an  economy. 

T53 


PART  X 
LIGHTING  OF   HOSPITALS  AND  DENTAL 

OFFICES 

Wards 

The  ward  is  essentially  a  sick  room  for  accommodating  a 
number  of  patients  at  the  same  time.  The  size  is  determined 
largely  by  the  purpose  for  which  the  hospital  is  used.  In  private 


Fig.    1— Sketch    Showing    Typical    Arrangement    of    Outlets    in    Wards    of 

.the    Square   and    Rectangular   Type.     Ceiling   outlets    for    general 

illumination   and   baseboard    receptacles    for   local    lighting, 

together  with  a  drop  lamp  over  the  nurse's  or 

attendant's  desk  will  be  noted 

hospitals,  most  of  the  patients  occupy  private  or  semi-private 
rooms,  and  the  wards  are  designed  to  accommodate  only  a  few 
patients.  Public  institutions,  however,  as  a  rule,  are  composed 
entirely  of  large  wards  accomimodating  upward  of  40  patients. 

Wards,  therefore,  vary  in  size  and  shape,  but  generally  are 
provided  with  hard  surfaced  walls  and  ceiling  of  light  color  and 
floors  of  glazed  surface  which  may  be  readily  cleaned.  Typical 
wards  of  square  and  rectangular  shapes  with  the  usual  arrange- 
ments of  beds  are  shown  in  Fig.  i. 

iS4 


Owing  to  the  fact  that  patients'  eyes  are  directed  toward  the 
ceiling  for  hours  at  a  time,  the  lighting  must  be  of  a  nature  that 
will  not  strain  or  tire  the  eye. 

In  the  ward  there  are  three  distinct  requirements  for  lighting 
as  outlined  below : 

(A)  In  the  evening  hours,  visitors  are  received  who  desire  to 
move  about  or  sit  and  talk  with  the  patients;  at  this  time  also, 
nurses  and  doctors  perform  their  routine  duties  in  preparation 
for  the  night. 

A  well  diffused  system  of  general  illumination  is  necessary  to 
provide  lighting  that  will  be  sufficient  for  the  ordinary  purposes 
as  described  above. 

(B)  Local  lights  over  the  beds,  additional  to  the  general 
system  are  necessary.    These  should  be  of  a  character  which  will 
permit  the  patients  to  read  or  pass  the  time  at  other  occupations 
requiring  close  vision,  without  eye  strain.     It  also  is  frequently 
necessary  for  the  doctors  or  nurses  to  attend  a  patient  at  night 
and  they  need  a  high  intensity  of  illumination  for  the  use  of  in- 
struments, etc. 

(C)  All  hospitals  require  the  lights  in  wards  to  be  extin- 
guished after  a  certain  hour,  but  a  night  light  is  necessary  to  en- 
able the  nurse  or  others  to  move  about  with  ease  and  exercise 
(he  necessary  supervision. 

Analyzing  these  requirements  we  find  that  the  totally  indi- 
rect system  is  probably  most  suitable  for  the  general  illumina- 
tion, although  semi-indirect  units  may  be  used  if  equipped  with 
heavy  density  bowls.  The  direct  method  using  totally  enclos- 
ing globes  may  be  utilized  in  small  wards  or  in  remodeled  build- 
ings where  conditions  are  not  favorable  for  indirect  lighting. 

Two  or  more  rows  of  ceiling  outlets  are  necessary  to  provide 
even  distribution  of  general  illumination  in  wards  which  are 
square  in  shape  but  the  long  narrow  type  require  only  a  single 
row  of  fixtures  as  shown  in  the  diagram,  Fig.  I. 

The  proper  intensity  of  general  illumination  for  wards  has 
been  the  subject  for  considerable  discussion.  The  consensus  of 
opinion,  however,  is  that  an  intensity  of  two  foot-candles  on  the 
bed  level  is  desirable. 

If  the  indirect  system  is  used  with  light  surroundings  the 
above  intensity  will  be  obtained  by  an  allowance  of  one-half  watt 
per  square  foot  floor  area.  If  surroundings  are  dark  this  should 
be  increased  slightly. 


Outlets  with  a  bracket  type  fixture  for  local  lighting  should 
be  provided  over  or  between  the  beds  to  furnish  sufficient  illu- 
mination for  special  purposes,  as  explained  above. 

There  are  several  type  of  wall  bracket  fixtures  available  for 
this  purpose.  One  fixture  which  reduces  wiring  costs  and  is  very 
desirable  combines  the  light  and  an  extra  receptacle  in  the  same 
base.  This  base  of  flat  white  glass  is  attached  to  the  wall;  an 
opalescent  reflector  conceals  the  source  and  directs  the  light  on 
the  bed.  Below  the  lamp  is  located  a  flush  receptacle  to  which 
portable  lamps,  heating  appliances,  or  instruments  may  be  at- 
tached. 

The  importance  of  providing  an  extra  receptacle  cannot  be 
over-emphasized.  It  is  obviously  undesirable  to  remove  the  lamp 
from  the  lighting  fixture  every  time  current  is  desired  for  these 
purposes  and  unless  equipment  such  as  that  just  described  is 
provided,  baseboard  outlets  at  frequent  intervals  are  essential. 

A  common  method  of  providing  the  night  lighting  is  by  use 
of  low  wattage  lamps,  wired  on  a  separate  circuit  in  the  fixtures 
for  general  illumination,  which  are  kept  burning  when  all  other 
lights  are  out.  A  very  modern  method  for  night  lighting  of 
wards  is  the  placing  of  lights  in  the  floor  within  trough  reflect- 
ors, covered  by  clear  plate  glass.  Their  light  is,  of  course,  sent 
to  the  ceiling  and  diffused  dowtnward.  This  arrangement  gives  a 
light  of  low  intensity  and  precludes  all  possibility  of  annoyingly 
bright  fixtures. 

A  somewhat  more  elaborate  night  lighting  system  uses  indi- 
vidual floor  lights  such  as  found  in  the  modern  Pullman  sleeping 
cars.  Small  pockets  lined  with  reflecting  material  are  recessed 
in  the  baseboard.  The  light  from  low  wattage  lamps  shining 
through  a  set  of  baffles  or  louvres  is  cast  in  a  narrow  streak  onto 
the  floor  between  the  beds,  not  visible  to  the  patient,  yet  making 
all  objects  readily  discernible. 

As  a  night  light  is  intended  to  furnish  just  enough  light  to 
discern  the  large  objects,  such  as  beds  and  doors,  an  intensity  of 
one-quarter  foot-candle  is  sufficient.  An  allowance  of  one-tenth 
watt  per  square  foot  floor  area  will  give  this.  Thus  in  the  sketch, 
Fig.  1,  of  the  square  ward,  the  dimensions  30  by  30  give  a  total 
area  of  900  square  feet,  an  allowance  of  one-tenth  watt  per 
square  foot  would  indicate  that  a  total  of  90  watts  was  required 
for  night  lighting/  A  25-watt  MAZDA  lamp  in  each  of  the  four 
indirect  units  .>hown  is  the  solution. 

156 


The  location  of  the  nurse's  desk  is  generally  at  some  conven- 
ient place  near  the  entrance,  and  an  outlet  should  be  provided  for 
a  portable  desk  light  to  be  used  by  the  night  nurse  in  making  up 
the  records,  etc.  A  wall  bracket  or  other  suitable  light  should 
also  be  provided  over  the  chart  rack  to  permit  its  examination 
at  night. 

The  medicine  cabinet  should  be  provided  with  suitable  light 
during  the  night  so  that  the  nurse  may  select  the  proper  contain- 
er without  groping  or  making  mistakes.  The  medicine  cabinet  is 
sometimes  placed  under  a  fixture  and  a  drop  light  with  rather 
dense  translucent  reflector  is  suspended  over  its  glass  top. 
Private  Room 

The  private  room  in  the  hospital  resembles  a  bedroom  which 
has  been  especially  equipped  for  the  care  of  the  sick.  In  many 
instances  it  is  highly  decorated  with  luxurious  surroundings, 
similar  to  one  in  a  private  residence. 

A  well  diffused  general  illumination  and  local  illumination 
similar  to  that  previously  described  may  be  used.  The  intensity 
need  not  be  so  high  as  in  the  ward  owing  to  the  fact  that  it  is 
used  by  fewer  persons.  The  fixtures  employed  in  lighting  may 
be  somewhat  elaborate  and  decorative  to  suit  any  particular  in- 
terior. The  indirect  systems  are  preferable  for  general  illumina- 
tion where  conditions  are  favorable. 

The  direct  system  may  also  be  used  for  this  purpose,  where 
indirect  methods  are  not  practical,  care  being  taken  to  provide 
suitable  diffusing  media.  A  central  ceiling  fixture  should  be  sup- 
plemented by  wall  brackets  or  table  lamps  near  the  bed.  These 
should  be  fitted  with  reflectors  or  decorative  shades  which  will 
diffuse  and  direct  the  light  where  needed. 

Corridors 

The  hospital  corridors  or  passage  ways  are  usually  provided 
with  hard  surfaced  "walls,  ceilings  of  light  color,  and  white  tile 
floors  which  can  be  readily  cleaned,  md  to  be  in  keeping  with  the 
modern  sanitary  conditions,  the  lighting  fixtures  should  be  of  a 
simple  construction,  easily  cleaned,  and  no-dust  collecting.  They 
should  be  so  arranged  that  direct  rays  will  not  strike  the  eyes  of 
the  patients  and  cause  annoyance. 

The  totally  indirect  method  is  very  desirable  for  lighting 
corridors  of  buildings  where  the  highest  standards  prevail;  the 
lighting  is  comfortable  and  artistic. 

The  system  of  direct  lighting,  employing  a  compact  ceiling 


fixture  with  a  suitable  diffusing  reflector  also  furnishes  good 
illumination  and  is  widely  used  for  corridor  lighting.  There  are 
many  types  of  sanitary  fixtures  designed  exclusively  for  hospital 
use,  being  dust-proof,  with  enamel  finish. 

As  only  sufficient  light  need  be  furnished  to  permit  easy  pas- 
sage, an  intensity  of  one  foot-candle  is  adequate.  For  direct 
lighting  an  allowance  of  one-quarter  watt  per  square  foot  will 
give  the  required  illumination,  providing  surroundings  are  light 
'.n  color.  This  value  should  be  increased  slightly  if  surround- 
ngs  are  dark. 

Operating  Rooms 

The  lighting  requirements  discussed  thus  far  do  not  differ 
materially  from  those  ordinarily  encountered.  In  the  surgery, 
however,  very  special  demands  exist  as  to  lighting. 

There  are  two  general  types  of  operating  rooms  which  require 
slightly  different  treatment  in  their  lighting.  The  first  is  the  type 
of  room  used  in  the  city  or  private  hospital,  which  is  relatively 
small  in  size  and  contains  merely  the  operating  table,  sterilizer, 
and  a  few  necessary  pieces  of  apparatus.  The  second  is  the  op- 
erating room  of  the  hospital  connected  with  some  educational  in- 
stitution and  is  made  in  the  form  of  an  auditorium  for  the  pur- 
pose of  holding  lectures  or  clinics  accompanied  by  demonstra- 
tions. Walls  and  ceiling  are,  or  should  be,  pure  white  and  in  the 
more  modern  hospitals,  the  walls  are  constructed  of  tiling  and 
the  floor  of  smooth  white  marble  for  ease  of  cleaning  and  sani- 
tation. 

In  the  first  type  of  room,  strong  illumination  is  needed  over  the 
operating  table  with  local  lighting  for  the  sterilizer  and  accessory 
appliances.  There  will,  in  general,  be  sufficient  light  reflected 
from  these  units  to  enable  the  surgeon  and  attendants  to  move 
about  With  facility. 

In  the  auditorium  type  of  operating  room,  the  "pit"  may  be 
treated  as  just  discussed,  but  general  illumination  must  also  be 
provided  in  the  balcony  to  enable  the  class  to  take  notes  with 
ease.  An  intensity  of  three  or  more  foot-candles  is  desirable 
here  and  may  be  provided  by  the  use  of  wall  brackets  at  the  rear 
of  the  top  tier  of  seats,  supplemented  by  properly  spaced  ceiling 
units  of  standard  types.  Wall  bracket  or  overhead  units  should 
plso  be  provided  for  general  illumination  of  the  "pit"  to  be  used 
when  preparing  for  an  operation  and  at  other  times  when  general 
illumination  is  necessary  here. 

158 


The  lighting  equipment  used  in  the  operating  room  must  have 
the  general  sanitary  and  ease  of  cleaning  qualities  necessary 
throughout  the  hospital. 

The  main  question  is  that  of  lighting  the  operating  table 
proper  and  the  requirements  for  both  types  of  room  are  identical 
in  this  respect.  In  the  auditorium  type  of  operating  room  it  is 
common  practice  to  conduct  operations  at  night  making  the  de- 
mands for  this  class  of  buildings  especially  important.  In  the 
smaller  institutions,  the  majority  of  the  operations  are  performed 


The    Operating    Amphitheater    of    a    Large    Municipal    Hospital.      The 

concentrating  reflectors  with  6o-watt  MAZDA  lamps  direct  the  light 

at  the  working  point 

in  the  daytime  and  it  is  only  on  special  occasions  or  emergencies 
that  artificial  light  is  called  into  play. 

The  operating  table  requires  a  very  high  intensity  of  well 
diffused  light  of  the  proper  color  coming  from  several  directions. 
High  intensity  is  required  on  account  of  the  minute  details  which 
must  be  observed  at  all  times.  Diffusion  is  necessary  to  elimi- 
nate shadow  effects.  Light  of  approximate  daylight  color  is  de- 
sirable in  order  that  the  blue  veins,  red  arteries,  or  yellow  bile 
ducts  can  be  distinguished  one  from  the  other.  It  is  also  essen- 
tial to  have  light  coming  from  several  directions  in  order  to  il- 
luminate the  interior  of  an  incision  properly.  Many  classes  of 
work  require  light  from  nearly  a  horizontal  direction  for  pene- 
tration. 

159 


The  fixture  itself  must  be  of  such  construction  that  there  is 
no  danger  of  dirt  accumulating  and  falling  into  the  wound,  and 
must  be  so  placed  as  to  minimize  the  possibility  of  this  action. 
It  should  radiate  the  minimum  amount  of  heat  in  order  that  the 
surgeon  and  attendants  may  work  in  comfort  and  without  dan- 
ger of  perspiring. 

The  natural  illumination  of  the  operating  room  should  be  a 
subject  of  careful  study  and  to  secure  the  best  results  the  surgery 
is  usually  located  on  the  north  side  of  the  top  floor  of  the  insti- 
tution where  minimum  obstructions  exist.  Skylights  with  semi- 
diffusing  glass  constitute  a  part  of  the  north  wall  and  a  consid- 
erable part  of  the  ceiling.  North  light  is  generally  well  diffused 
and  more  uniform  in  quality  and  quantity  than  that  from  other 
points  of  the  compass,  and  for  this  reason  is  preferred. 

The  surgeon  endeavors  to  conduct  the  most  imfportant  opera- 
tions under  daylight  conditions,  yet  he  realizes  that  in  times  of 
emergency  dependence  must  be  had  on  artifiical  illumination. 
Without  giving  the  matter  careful  thought,  many  medical  men 
would  make  the  claim  that  it  is  impossible  to  secure  thoroughly 
satisfactory  artificial  lighting.  This  statement  may  be  justly 
combated,  for  with  discretion  in  the  choice  of  equipment  and 
with  the  application  of  sufficient  electrical  energy  transforme;! 
into  light,  daylight  effects  can  be  readily  simulated.  The  unin- 
itiated might  think  that  such  a  procedure  was  too  costly  to  be 
practical.  Such  is  not  the  case.  Suppose,  for  example,  it  re- 
quired a  total  of  3,000  to  5,000  w'atts  to  illuminate  an  operating 
room  properly.  (This  is  far  more  than  necessary  in  most  cases.) 
At  the  customary  rates  for  electrical  energy,  this  might  cost 
from  25  to  50  cents  an  hour.  The  operating  room  is  customarily 
charged  for  and  it  will  be  seen  that  this  figure  represents  but  i 
to  2  per  cent  of  the  rental  of  the  room.  Certainly  proper  lighting 
is  worth  this  percentage. 

North  skylight  can  be  imitated  by  placing  daylight  MAZDA 
lamps  in  suitable  reflectors  outside  of,  and  above  the  skylight,  il- 
luminating the  room  with  light  of  the  same  character,  of  the 
same  general  d'rection  and  with  sufficient  intensity.  This  meth- 
od is  actually  used  in  some  of  the  more  modern  buildings.  It  is 
true  that  there  is  a  certain  amount  of  absorption  in  transmission 
through  the  glass  and  that  the  construction  work  is  rather  cost- 
ly, but  the  splendid  results  obtained  justify  such  expenditures. 
For  general  illumination  of  this  character  an  intensity  of  30  to 

160 


50  foot-candles  is  desirable  and  would  be  attained  by  provid 
mg  from  10  to  15  watts  per  square  foot  of  floor  area  depending 
en  the  structural  arrangement,  density  of  the  glass  of  the  sky- 
light, type  of  reflector,  size  of  lamp  used,  and  similar  details. 


Fig.  2.     Arrangement  of  Angle  Type   Prismatic   Reflectors  with  75-watt 

Bowl   Enameled   Daylight  MAZDA  lamps   for  Illuminating 

the  Operating  Table 

If  such  a  scheme  as  this  is  not  feasible,  a  number  of  other 
methods  represent  good  practice.  Totally  indirect  illumination 
may  be  used  if  the  ceiling  is  light  in  color  and  of  a  character 
suitable  for  reflecting  the  light.  Mirrored  glass  units  equipped 
with  daylight  MAZDA  lamps  are  efficient  and  produce  evenly 
distributed,  very  well  diffused  (practically  shadowless)  illumina- 
tion. Instances  have  been  reported  where  indirect  lighting  has 
proven  unsatisfactory  for  this  purpose  but  analysis  generally 
reveals  that  inefficient  wattage  was  used  and  hence  an  inade- 
quate intensity  of  illumination  secured.  It  must  be  borne  in 
mind  that  work  of  the  character  carried  on  in  the  surgery  de- 
mands a  high  degree  of  illumination  and  to  secure  this,  sufficient 
power  must  be  used. 

Where   conditions   preclude  the  application   of  the  skylight 
method  of  general  illumination  by  the  indirect  systems,  special 

161 


direct  lighting  fixtures  are  available.  Such  a  device  provides 
diffused  light  of  a  high  intensity  from  directly  above  the  table. 
The  large  area  of  the  source  tends  to  eliminate  shadows,  has 
the  advantage  of  simplicity  and  compactness.  A  unit  of  this 
character  is  entirely  adequate  for  the  less  exacting  operations 
and  maternity  work.  It  is  often  necessary  to  supplement  a  unit 
of  this  type  with  a  portable  lamp  stand  and  suitable  reflector  to 
direct  light  on  vertical  surfaces. 

In  the  attempt  to  obtain  light  from  a  number  of  directions 
twelve  prismatic  angle  type  reflectors  are  mounted  on  a  frame- 
work or  directly  attached  to  the  ceiling  about  10  feet  above  the 
floor.  These  are  fitted  with  75-watt  bowl  enameled  daylight 
MAZDA  lamps.  A  splendid  distribution  of  light  on  the  table  from 
all  directions  is  secured.  The  light  is  of  a  suitable  quality,  units 
are  hung  at  a  rufficient  height  so  that  the  heat  is  not  objection- 
able, the  fixture  construction  is  simple  and  reflectors  are  not  lo- 
cated directly  above  the  table  and  any  dust  which  might  have 
accumulated  will  not  fall  in  the  wound.  Since  the  prismatic  re- 
flectors transmit  a  certain  percentage  of  the  light  no  general  il- 
lumination is  needed  in  addition.  Measurements  of  the  illumi- 
nation produced  by  such  a  layout  indicate  the  following  intensi- 
ties :  between  40  and  50  foot-candles  on  the  horizontal  plane, 
from  20  to  30  foot-candles  on  the  45  degree  plane  and  from  10 
to  20  foot-candles  on  vertical  surfaces  above  the  table. 

Wiring  and  Signal  Systems 

The  source  of  current  supply  in  any  public  building  must 
be  dependable.  This  is  particularly  important  in  the  hospital 
where  the  occupants  are  in  a  critical  physical  condition.  The 
most  exacting  demands  exist  in  the  operating  room  where  the 
failure  of  illumination  might  have  a  fatal  result. 

Whether  the  hospital  has  its  own  plant  or  whether  the 
current  is  supplied  by  a  Central  Station,  the  building  should  be 
so  wiired  that  the  blowing  of  a  fuse  will  not  extinguish  all  of 
the  lights  in  any  section  of  the  building.  The  circuits  in  wards 
and  corridors,  for  example,  should  be  so  arranged  that  part 
of  the  lights  are  on  one  circuit  and  part  on  another.  In  some 
instances,  duplicate  panel  boards  with  emergency  switching 
and  plugging  arrangements  are  installed  to  make  possible  a 
quick  change  over. 

An  emergency  system  in  the  operating  room  is  particularly 
important  so  that  even  the  failure  of  the  entire  electric  supply 

162 


will  not  throw  the  room  into  darkness.  Gas  as  an  auxiliary 
is  at  best  a  makeshift  for  it  is  not  likely  that  suitable  equip- 
ment will  be  installed  to  give  satisfactory  illumination  with 
gas.  As  ether  is  used  as  an  anaesthetic,  it  is  not  particularly 
safe  to  have  an  open  flame  near  the  spot  where  this  is  being 
administered.  A  small  storage  battery  of  sufficient  capacity  to 
light  the  operating  room  for  a  given  period  of  time  is  a  most 
desirable  feature.  The  mere  throw  of  a  switch  in  such  an  in- 
stallation takes  care  of  any  emergency.  The  care  required  by 
a  storage  battery  is  not  excessive  and  most  hospitals  have  a 
plant  engineer  who  is  thoroughly  competent  to  maintain  the 
battery.  Smaller  lower  voltage  batteries  are  also  very  useful 
for  furnishing  current  for  miniature  surgical  lamps  and  mi- 
croscope illumination. 

The  signal  system  in  the  hospital,  an  important  element,  also 
employs  the  storage  battery  for  its  operation.  The  modern  type 
of  signal  devices  are  noiseless  and  the  old  bell  or  buzzer  for 
calling  the  nurse  or  attendant  is  a  thing  of  the  past.  Two  gen- 
eral methods  are  employed  for  the  purpose,  one  utilizes  a  sema- 
phore or  small  arm  which  drops  from  a  vertical  to  horizontal 
position  over  the  door  or  nurse's  desk.  The  latest  system1  has 
a  push  button  by  the  patient's  bed  which  when  operated  lights 
a  signal  lamp  over  the  nurse's  desk  and  one  by  the  bed,  or 
outside  of  the  door  in  the  case  of  a  private  room.  When  the 
signal  lights,  the  nurse  glances  down  the  ward  or  corridor  and 
locates  the  patient  who  requires  attention.  These  lights  are 
left  burning  until  the  nurse  responds,  who  extinguishes  them 
by  inserting  a  special  key  in  the  push  button  switch.  This 
system  is  not  so  unsightly  and  not  as  likely  to  get  out  of  order 
as  the  semaphore  or  annunciator  system. 

Dental  Offices 

The  waiting  room  of  a  dental  office  and  the  reception  room  of 
a  hospital  present  similar  lighting  problems.  The  more  attrac- 
tive and  soothing  the  lighting  conditions  are  made,  the  more 
readily  the  patient  will  await  his  appointment.  Floor  and  table 
lamps  may  be  used  to  supplement  the  general  lighting  advan- 
tageously. 

There  are  two  systems  in  vogue  for  securing  proper  illu- 
mination in  the  office  for  the  actual  dental  work;  one  supplies 
a  high  intensity  of  general  illumination  enabling  the  dentist  to 
work  under  conditions  approximating  natural  lighting  and  the 

163 


other  involves  the  use  of  only  a  small  beam  of  light  focused 
directly  upon  the  mouth  by  some  form  of  special  illuminator 
or  spot  lamp.  As  with  any  class  of  lighting,  general  illumina- 
tion is  more  effective  in  most  cases  and  offers  wider  possibilities. 

It  is  obvious  that  the  desirable  results  are  secured  with  such 
a  system  when,  no  matter  where  the  dentist  is  standing  or  work- 
ing, neither  he  nor  his  instruments  will  cast  shadows 
on  the  working  point.  The  ideal  light  would  reach  every  por- 
tion of  the  mouth  and  with  the  assistance  of  the  mirror,  illu- 
minate the  deepest  recess.  In  order  to  minimize  shadow  effects, 
it  is  obvious  that  light  must  come  from  more  than  one  direc- 
tion which  necessitates  the  use  of  more  than  one  light  source  or 
a  unit  having  a  very  large  reflecting  or  diffusing  surface.  The 
Femi-indirect  and  totally  indirect  fixtures  which  direct  the  major 
portion  of  the  light  to  the  ceiling  produce  such  an  effect.  Since 
the  details  to  be  observed  are  extremely  minute,  high  intensity 
is  an  essential  element.  Since  the  color  of  teeth  must  be  com- 
pared and  the  condition  of  various  tissues  noted  light  approxi- 
mating daylight  is  desirable. 

Where  structural  considerations  prevent,  or  where  the  color 
of  surroundings  is  such  as  to  preclude  such  lighting,  its  effects 
can  be  simulated  by  the  use  of  an  adjustable  diffusing  fixture. 
Since  the  dentist  usually  wtorks  from  the  patient's  right  side, 
this  outlet  should  be  located  at  the  front  and  slightly  to  the 
left.  Where  the  fixture  is  adjustable,  the  swing  of  the  support- 
ing arm  should  be  regulated  for  this  position. 

A  fixture  having  the  same  general  characteristics  as  the  one 
described,  although  not  quite  so  simple,  utilizes  four  lamps  in 
prismatic  enclosing  globes  on  a  swinging  arm  fastened  to  the 
window  casing  The  simplicity  of  installation  of  these  units 
is  one  of  the  great  points  in  their  favor.  Otn  the  other  hand, 
a  certain  amount  of  time  is  involved  in  adjusting  the  device 
to  suit  particular  conditions,  which  is  not  necessary  with  the 
overhead  general  lighting  scheme. 

The  spot  lamp  falls  in  the  same  class  as  the  local  lamp  over 
the  tool  in  the  machine  shop.  It  is  inconvenient,  and  valuable 
time  is  wasted  in  adjusting  it.  Most  machine  shop  illumina- 
tion can  be  secured  much  better  from  the  high  intensity  general 
method,  yet  there  are  a  few  special  processes,  such  as  the  ma- 
chining of  the  interior  of  deep  castings  which  make  a  local  lamp 
a  necessity.  Just  so  in  the  dental  orfite.  The  greater  propor- 

164 


don  of  the  work  can  be  more  satisfactorily  performed  with 
proper  general  lighting,  yet  for  some  very  special  conditions, 
the  mouth  lamp  is  a  very  valuable  adjunct.  Continuing  the 
analogy,  many  forms  of  drop  lamps  in  the  industrial  plant 
are  practically  useless  and  objectionable  from  the  standpoint 
of  glare.  The  dental  lamp  which  employs  a  low  wattage  unit 
with  a  half  shade  reflector  on  a  flexible  or  adjustable  arm  throws 
much  light  in  the  patient's  eye,  is  cumbersome  and  if  not 
especially  constructed  may  soon  become  mechanically  weak. 
The  carefully  designed  lens  type  spot  lamp,  illuminated 


A     Small     Dental     Office     Lighted    by     Three     200-Watt     MAZDA     Daylight 

Lamps  in  Simple  Type  Semi-indirect  Bowls.     A  uniformly  distributed 

high   intensity  illumination   of   suitable   color   is   produced.     The 

diffused     character    of     the     light     is     particularly     valuable 

for  illuminating  the   recesses   of   the  mouth 

mouth  mirror  and  head  band  type  of  equipments,  not  only  keep 
the  stray  light  from  annoying  the  patient,  but  are  useful  in 
root  canal  work  and  for  trans-illumination  in  the  detection  of 
dead  teeth.  At  best,  the  local  lamp  is  only  an  accessory  and 
dependence  should  not  be  put  on  it  alone.  Good  general  illu- 
mination is  necessary  to  enable  the  operator  to  pick  up  readily 
any  instrument  on  his  stand  or  cabinet,  for  in  the  poorly  lighted 
room  the  contrast  between  a  brightly  illuminated  area  and  the 
dark  surroundings  is  a  source  of  much  confusion  to  the  eye. 

165 


PART  XI 
FLOOD-LIGHTING 

Dignity  and  beauty  combine  with  the  spectacular  to  provide 
in  flood  lighting  one  of  the  most  effective  forms  of  electrical 
display.  A  stately  building,  a  national  monument,  a  scene  of 
great  natural  beauty,  bathed  in  light  against  the  darkness  of  the 
night,  may  be  made  to  compel  attention  and  to  inspire  admira- 
tion. Without  a  suggestion  of  garishness,  yet  with  attracting 
power  which  is  irresistible,  flood  lighting  accomplishes  its  pur- 
pose. 

The  application  of  flood  lighting,  however,  is  not  limited  to 
the  producing  of  striking  and  unusual  effects.  There  are  many 
applications  for  it  in  industry.  The  time  required  for  outdoor 
construction  work  may  be  considerably  reduced  by  a  flood 
lighting  system  which  will  permit  work  to  be  continued  through- 
out the  night;  the  flood  lighting  of  railroad  yards,  docks, 
wharves,  and  the  yards  of  industrial  plants,  permits  night  work 
to  be  done  efficiently  and  with  increased  safety.  An  applica- 
tion is  found  in  the  lighting  of  traffic  intersections  to  facilitate 
the  movement  of  vehicles  and  pedestrians  and  to  promote  safety. 
The  illumination  of  large  outdoor  spaces  devoted  to  pageants 
or  sports,  including  bathing  beaches,  drill  grounds,  and  open- 
air  theatres,  is  being  most  satisfactorily  accomplished  by  flood 
lighting.  Bulletin  boards  and  painted  signs  located  high  up  on 
water  towers  or  chimneys  are  examples  of  the  application  of 
flood  lighting  to  electrical  advertising.  New  uses  are  being  con- 
stantly found  as  the  possibilities  of  this  form  of  lighting  are 
becoming  better  understood. 

The  Problem 

The  design  of  a  flood-lighting  installation  is  governed  by 
the  purpose  which  the  illumination  is  to  accomplish.  In  the 
case  of  a  bulletin  board  or  painted  sign,  the  aim  should  be  to 
provide  a  uniform  level  of  illumination  over  the  entire  surface 
of  the  display.  One  or  two  projectors,  if  properly  located,  will 
often  be  sufficient  for  this  purpose.  Outdoor  construction  work 
and  railway  and  industrial  yards  require,  of  course,  ample  light 
at  all  working  points  and  yard  thoroughfares,  but  of  very  great 
importance  is  the  requirement  that  long,  heavy  shadows,  which 
present  a  constant  menace  to  safety,  be  avoided.  This  requires 
that  light  be  received  from  several  directions  and  a  number  of 
projectors  located  advantageously  about  the  grounds  are  there- 
fore necessary.  The  flood  lighting  of  buildings  and  monuments 

166 


is  largely  a  problem  of  aesthetics.  Here  uniform,  shadowless 
lighting"  often  defeats  the  purpose  of  the  installation.  Shadows 
are  essential  to  relief,  and  contrasts  in  intensity  or  in  color  of 
light  can  be  used  advantageously  to  bring  out  important  details 
and  to  suppress  others;  extreme  care<jmust,  however,  be  exer- 
cised to  see  that  shadows  will  not  be  formed  which  distort  the 
appearance  of  the  structure  and  produce  a  grotesque  result. 
The  aim  should  be  to  light  the  surface  to  produce  the  most 


Fig.   1 — Typical   Floodlighting   Reflector    Contours 
A  and  B,  for  use  with  ordinary  multiple  MAZDA  C  lamps, 
give  moderate  and   wide  spread  of   beam. 

C,  D,  and  E  are  for  use  with  MAZDA  C  floodlighting  lamps 
C — Shallow  parabola,  narrow  spread  of  beam 

D,  E — Deep  reflectors,  moderate  spread  of  beam 

pleasing  and  desirable  effect.    To  permit  this  to  be  done,  a  num- 
ber of  units,  or  banks  of  units,  are  required. 
Flood  Lighting  Equipment 

Since  a  specularly  reflecting  surface  is  necessary  in  order  to 
direct  the  light  into  a  relatively  narrow  beam,  as  is  desired  for 
flood  lighting,  polished-metal  or  mirrored-glass  reflectors  must 
be  employed  in  such  equipments.  Because  of  their  high  initial 
reflection  factors  and  maintenance  of  efficiency  in  service,  the 
mirrored-glass  units  have  been  widely  adopted. 

167 


Fig.  2 — Typical  Projectors  for  Use  with  Ordinary  Multiple  MAZDA  C  Lamps 


Fig.  3 — Typical  Distributions  of  Light  Flux 
from  Units  of  this  Class.     Circles  rep- 
resent   relative    areas    of    surfaces 
illuminated 

A — Medium    spread    of    beam 
B — Wide  spread  of  beam 


Note — With  some  floodlighting  equipments,  several  reflectors  giving  beams 
of  various  concentrations  are  interchangeable  in  one  housing. 

168 


Fig.  A — Typical  Projectors  for  Use  with  MAZDA  C  Floodlighting  Lamps 


Fig.  5 — Typical  Distribution  of  Light  Flux  from  Units  of  this  Class 
Circles  represent  relative  areas  of  surfaces  illuminated 

A — Narrow  spread  of  beam 
B — Medium  spread  of  beam 
C — Wide  spread  of  beam 

Note — With  some  floodlighting  equipments,  several  reflectors  giving  beams 
of  various  concentrations  are  interchangeable  in  one  housing. 

169 


The  equipments  available  may  be  divided  into  two  general 
classes :  those  which  in  various  sizes  employ  100  to  1000  watt 
Mazda  C  lamps  of  the  regular  construction  and  those  which  are 
designed  for  use  with  flood-lighting  lamps,  having  specially  con- 
centrated filaments,  of  the  250  or  500  watt  sizes.  The  smaller 
light  source  of  the  latter  permits  more  accurate  control  of  the 
beam.  The  use  of  the  former  equipments  simplifies  the  stocking 
and  supplying  of  lamps.  One  limitation  in  their  use  is  the  fact 
that  the  larger  sizes  of  Mazda  C  lamps  should  not  be  operated 
with  the  tip  tilted  more  than  30  degrees  from  vertically  down- 
ward.* On  the  other  hand,  the  concentrated  filament  flood-light- 
ing lamps  are  so  constructed  that  they  may  be  operated  at  any 
angle  except  within  45  degrees  of  vertically  tip  downward.  The 
equipments  using  these  lamps  usually  have  the  axis  of  the  lamp 
in  the  axis  of  the  reflector. 

The  spread  of  the  light  from  a  projector,  that  is,  the  angle 
of  divergence  of  the  beam,  depends  upon  the  size  of  the  source 
and  its  distance  from  the  reflecting  surface  (in  other  words,  the 
angle  which  the  light  source  intercepts  at  the  reflector)  and  upon 
the  contour  of  the  surface.  Obviously,  the  narrower  beam  of 
light  can  be  obtained  with  the  concentrated-filament  flood- 
lighting lamps.  Equipments  employing  these  are  available  with 
a  beam  spread  of  as  low  as  8  degrees,  and  in  other  designs,  of 
as  high  as  50  degrees.  With  the  ordinary  multiple  lamp  equip- 
ments, the  minimum  spread  of  beam  is  about  15  degrees  and 
the  maximum  about  50  degrees.  With  a  given  contour  of 
reflector,  some  variation  in  the  spread  of  beam  is  obtained  by 
moving  the  lamp  filament  backward  or  forward  along  the  axis 
of  the  reflector.  The  maximum  spread  so  obtainable  is  usually 
less  than  twice  the  minimum  angle  of  divergence. 

The  percentage  of  the  light  from  the  lamp  directed  into  the 
beam  depends  primarily  upon  the  amount  intercepted  by  the 
reflector  and  also  upon  the  contour  of  its  surface.  The  equip- 
ments available  direct  from  20  to  50  per  cent  of  the  light  into 
the  beam.  For  all  ordinary  multiple  lamp  equipments,  how- 
ever, and  for  the  flood  lighting  lamp  projectors  of  medium  and 
wide  beams,  an  output  of  40  to  50  per  cent  may  be  obtained  with 
reflectors  of  proper  design.  Fig.  1  shows  typical  designs  of 
the  reflectors  for  both  the  regular  and  flood-lighting  lamp  equip- 
ments. 


*  For  any  other  position  of  burning,  lamps  must  be  specially  ordered. 

170 


TABLE  No.   1 

FLOOD    LIGHT    CALCULATION    DATA 


c 

Deg. 

2B  =  8° 

2  B  =  12° 

H 
Feet 

L 
Feet 

W 

Feet 

A 
Sq.  Ft. 

L 
Feet 

W 
Feet 

A 

Sq.  Ft. 

25 

0 
15 
30 

45 
60 
75 

3.50 
3.75 
4.67 
7.03 
14.19 
56.01 

3.50 
3.62 
4.04 
4.96 
7.04 
13.98 

10 
11 
15 

27 
79 
615 

5.26 
5.64 
7.03 
13.13 
21.73 
92.72 

5.26 
5.44 
6.08 
9.23 
10.08 
22.23 

22 
24 
32 
95 
172 
1619 

50 

0 
15 
30 

45 
60 
75 

6.93 
7.50 
9.34 
14.06 
28.39 
112.02 

6.93 
7.24 
8.08 
9.91 
14.09 
27.95 

38 
43 
57 
109 
314 
2459 

10.51 
11.27 
14.06 
26.26 

43.45 
185.44 

10.51 
10.89 
12.16 
18.46 
20.17 
44.46 

87 
96 
130 
381 
688 
6476 

75 

0 
15 
30 

45 
60 

75 

10.49 
11.25 
14.01 
21.08 
42.58 
168.03 

10.49 
10.86 
12.12 
14.87 
21.13 
41.93 

86 
96 
133 

246 
707 

5533 

15.77 
16.91 
21.10 
39.38 
65.18 
278.15 

15.77 
16.33 
18.24 
27.70 
30.25 
66.69 

195 
217 
292 
857 
1548 
14567 

100 

0 
15 
30 

45 
60 

75 

13.99 
15.00 
18.69 
28.11 

57.77 
324.04 

13.99 
14.48 
16.16 
19.83 
28.18 
55.90 

154 
171 
237 
438 
1256 
9836 

21.02 
22.55 
28.13 
52.51 
86.90 
370.87 

21.02 
21.77 
24.32 
36.93 
40.33 
88.92 

370 
386 
518 
1523 
2753 
25902 

171 


TABLE   No.    1 
(Continued.) 

FLOOD    LIGHT    CALCULATION    DATA 


2  B  =  16° 

2  B  =  20° 

H 
Feet 

C 
De*. 

L 
Feet 

W 
Feet 

A 

Sq.  Ft. 

L 
Feet 

W 
Feet 

A 

Sq.  Ft. 

25 

0 
15 
30 

45 
60 

75 

7.03 
7.54 
9.43 
14.34 
29.86 
114.71 

7.03 
7.29 
8.14 
10.03 
14.53 
31.91 

39 
43 
60 
113 
342 
3633 

8.82 
9.45 
11.88 
18.20 
38.90 
232.14 

8.82 
9.12 
10.24 
11.38 
18.52 
45.25 

61 
68 
95 
181 
566 
8251 

50 

0 
15 
30 

45 
60 

75 

14.05 
15.08 
18.86 
28.67 
59.71 
229.42 

14.05 
14.58 
16.28 
20.06 
29.06 
63.80 

155 
170 
241 
452 
1367 
14531 

17.63 
18.89 
23.76 
36.40 

77.79 
464.28 

17.63 
18.23 
20.47 
22.76 
37.04 
90.50 

244 
271 
382 
724 
2263 
33002 

75 

0 
15 
30 

45 
60 
75 

21.08 
22.63 
26.29 
43.01 
89.57 
344.13 

21.08 
21.88 
24.42 
30.09 
43.58 
65.80 

349 
383 
543 
1016 
3076 
32694 

26.45 
28.34 
35.63 
54.59 
116.68 
696.41 

26.45 
27.35 
30.71 
34.14 
55.55 
135.76 

549 
609 
859 
1629 
5091 
74255 

100 

0 
15 
30 

45 
60 

75 

28.11 
30.17 
37.73 
57.35 
119.42 
458.84 

28.11 
29.17 
32.56 
40.12 
58.11 
127.61 

641 
680 
965 
1807 
5468 
58122 

35.27 
37.79 
47.51 
72.79 

155.57 
928.55 

35.27 
36.46 
40.95 
45.52 
74.07 
181.01 

977 
1082 
1528 
2896 
9050 
132009 

Flood  Lighting  Design  Data 

Four  factors  must  be  considered  in  the  design  of  a  flood- 
lighting installation.  These  are: 

1 — Location  of  equipment; 

2 — Choice  of  equipment; 

3 — Illumination  desired ; 

^ — Size  and  number  of  units. 

Location  of   Equipment 

The  necessity,  in  many  cases,  of  locating  the  lighting  units 
where  they  will  be  inconspicuous,  as  in  the  lighting  of  monu- 
ments, frequently  leaves  little  choice  of  position.  Advantage 
may  be  taken  of  neighboring  buildings,  columns,  porches,  and 
ledges  on  the  structure  itself,  neighboring  trees,  and  other  pos- 
sibilities which  suggest  themselves  in  each  particular  problem. 
Similar  locations  may  be  used  for  the  lighting  of  bulletin  boards 
and  painted  signs. 


172 


TABLE   No.    1 
(Continued.) 

FLOOD    LIGHT    CALCULATION    DATA 


A 

2  B  =  30° 

2  B  =  50° 

H 
Feet 

c 

Deg. 

L 
Feet 

W 
Feet 

A 

-  Sq.  Ft. 

L 
Feet 

W 
Feet 

A 
Sq.  Ft. 

25 

0 

15 
30 

45 
60 

75 

13.40 
14.43 
18.30 
29.64 
68.30 

13.40 
13.91 
15.66 
20.19 
30.25 

141 
158 
226 
456 
1623 

23.42 
25.39 
33.52 
59.64 
268.24 

23.42 
24.33 
27.95 
37.31 
79.07 

431 
486 
826 
1747 
16659 

50 

0 
15 
30 
45 
60 
75 

26.80 
28.87 
36.60 
59.29 
136.61 

26.80 
27.81 
31.32 
40.39 
60.49 

564 
631 
902 
1825 
6490 

46.83 
50.77 
67.03 
119.28 
536.49 

46.83 
48.66 
55.91 
74.61 
158.15 

1722 

1944 
3302 
,  6990 
•66638 

75 

0 

15 
30 
45 
60 

75 

40.19 
43.30 
54.90 
88.93 
204.91 

40.19 
41.72 
46.97 
60.58 
90.74 

1269 
1419 
2030 
4107  ' 
14603 

70.25 
76.16 
105.46 
178.91 
804.73 

70.25 
72.99 
83.86 
111.92 
237.22 

3875 
4374 
7430 
15727 
149935 

100 

0 

15 
30 

45 
60 

75 

53.59 
57.74 
73.21 
118.57 
273.21 

53.59 
55.62 
62.63 
80.78 
120.99 

2256 
2522 
3609 
7301 
25961 

93.66 
101.54 
134.06 
283.55 
1072.98 

93.66 
97.32 
111.81 
149.23 
316.30 

6890 
7776 
13092 
27959 
266551 

TABLE   No.   2 

WATTS    PER    SQUARE    FOOT    RECOMMENDED    FOR    FLOOD    LIGHTING 

Poorly  Brightly 

Illuminated  Illuminated 

Subject  to  be  Illuminated  Surroundings  Surroundings 

Buildings  and  Monuments : 

White  or  Cream 0.50—1.00  0.75—1.50 

Light  Yellow  and  Buff 0.75—1.50  1.50—3.00 

Medium  Buff  1.50—3.00  2.50—5.00 

Billboards    and    Painted    Signs 1.25—3.75  2.50—7.50 


Bathing  Beaches  

Buildings : 

Construction     

Excavation  

Docks,  Wharves  and  Bridges 

Drill  Grounds  

Outdoor  Athletics  :  Football  Practice,  etc . . 

Outdoor  Stage  

Playgrounds  

Yards  for  Mills,  Factories  and  Railroads.. 


0.05—0.5 

0.5  —1.00 
0.10—0.50 
0.25—0.75 
0.10—0.75 
0.50—1.50 
0.50—1.00 
0.25—0.75 
0.05—0.25 


173 


TABLE   No.   3. 

FOOT-CANDLE    ILLUMINATION    RECOMMENDED    FOR    FLOOD    LIGHTING 

Poorly  Brightly 

Illuminated  Illuminated 

Subject  to  be  Illuminated                               Surroundings  Surroundings 
Buildings  and  Monuments: 

White   or    Cream 2—4  6— 1> 

Light  Yellow  and  Buff 3—6  6—12 

Medium    Buff    6-12 

Billboards    and    Painted    Signs '— ^ 

Bathing  Beaches    0 .25— 2 

Buildings  : 

Construction     2 — 4 

Excavation    0  •  5 — 2 

Docks,   Wharves   and   Bridges —3 

Drill    Grounds    

Outdoor  Athletics:    Football   Practice,   etc..  2—6 

Outdoor    Stage    2—4 

Playgrounds     — 3 

Yards  for  Mills,  Factories  and  Railroads....  0.25—1 

TABLE    No.    4 

LUMEN   OUTPUT  OF  MAZDA  LAMPS    USED   FOR    FLOOD  LIGHTING 

Mazda  Lamps  of  the  Regular   Construction 
Watts  Lumen  Output 

100.. 1300 

150 2100 

200 3000 

300 4900 

500 9000 

750 14000 

1000 20000 

Mazda  Lamps  for  Flood  Lighting  Service 

250 3250 

500. .  8100 


In  the  lighting  of  yards  and  outdoor  construction  work,  units 
may  sometimes  be  located  on  surrounding  buildings,  poles,  or 
towers;  frequently,  however,  it  will  be  necessary  to  erect  poles 
especially  for  the  units  in  order  to  obtain  locations  which  will 
allow  light  to  be  delivered  from  sufficiently  different  angles  to 
destroy  dangerous  shadows.  In  order  to  avoid  serious  glare 
from  the  units,  the  projectors  should  be  mounted  high, — at  least 
30  feet  above  the  ground.  Mounting  heights  of  40,  50,  or  even 
60  feet  are  usually  to  be  preferred. 

Choice  of  Equipment 

The  choice  of  equipment  is  largely  determined  by  the  dimen- 
sions of  the  area  to  be  lighted  and  by  the  location  of  the  equip- 
ment with  respect  to  the  area.  Frequently,  two  or  more  forms 

J74 


Floodlighting    Liberty 

252,   250-watt    projectors    in    15    separate   banks    located 
as  shown  in  the  diagram  are  used  for  this  illumination 


Plan  of  Bedloe's  Island,  Showing  Location  and  Number  of  Lighting  Units 

175 


of  equipment  can  be  used  advantageously  for  a   single  instal- 
lation. 

The  beam  of  light  from  a  projector  is  conical  in  form  and 
hence  when  striking  a  surface  perpendicular  to  its  axis  illumin- 
ates a  circular  area.  If  the  beam  strikes  a  surface  at  an  angle, 
the  resultant  spot  of  light  is,  of  course,  elliptical  in  form.  By 
overlapping  the  beams  it  is  possible  to  obtain  an  approximately 
uniform  illumination  and  avoid  striations,  or  images  of  the  fila- 
ment, projected  by  the  specularly  reflecting  surface  of  the  reflec- 
tor. Ribbed  or  fluted  cover  glasses  are  available  by  which  the 
spread  of  the  beam  may  be  greatly  extended  in  one  direction. 

In  flood  lighting,  it  is  often  found  necessary  to  eliminate  spill 
light  in  order  to  avoid  glare  or  to  confine  the  light  to  a  certain 
definite  area.  For  this  purpose  some  manufacturers  supply  spill- 
shields  to  be  placed  within  the  projector  or  it  is  not  difficult  to 
equip  the  projectors  with  cylindrical  tubes  or  baffle  plates. 

Table  1  gives  the  dimensions  and  area  of  the  spot  illuminated 
by  projectors  having  various  spreads  of  beam  located  at  various 
distances  from  the  surface  illuminated  and  directing  the  light 
to  it  at  different  angles.  By  means  of  this  table,  the  location 
of  the  units  having  been  decided  upon,  the  choice  of  the  correct 
beam  spread  may  be  made  and  the  equipment  selected  accord- 
ingly. 

Illumination  Desired 

In  deciding  the  desirable  amount  of  illumination  for  the 
specific  installation  under  consideration,  it  is  necessary  to  take 
into  account  such  factors  as  the  color  of  the  surface  to  be  lighted 
or  the  nature  of  the  work  to  be  performed,  the  brightness  of  sur- 
roundings, and  in  the  case  of  advertising  displays,  the  attracting 
power  of  high  illumination.  There  is  seldom  danger  of  over- 
lighting  if  the  installation  is  properly  made.  On  the  other  hand, 
it  should  be  recognized  that  to  make  a  structure  stand  out  in 
the  midst  of  bright  surroundings,  light  must  be  projected  in 
quantity, — literally  layer  upon  layer;  halfway  measures  have  no 
place  in  flood  lighting  for  artistic  effect.  The  ideal  subject  for 
flood  lighting  is  the  one  of  great  beauty  in  an  isolated  spot. 
The  data  of  Tables  2  and  3  are  representative  of  modern 
practice,  although,  as  mentioned,  individual  conditions  will  lead 
to  considerable  departures  from  the  ranges  given.  Unques- 
tionably, the  use  of  higher  values  than  here  shown  is  desirable 
in  many  cases. 

176 


Size  and  Number  of  Units 

There  are  two  simple  methods  of  determining  the  size  and 
number  of  units  required,  first,  by  using  the  data  in  Table  2 


The  Wheatena  Factory,   Rahway,   New  Jersey — Lighted  with  32 

500-watt  projectors  with  an  average  of  only  0.41  watts  per 

square   foot 


A  typical  bank  of  projectors  used  to  light  the  Wheatena  Factory,  illustrating 

the  substantial  construction  of  mounting  frame,  which  is  made  of  2-inch  pipe 

set  in  concrete,   painted  dark  green  to  harmonize  with   surroundings 

which  gives  the  average  watts  per  square  foot  that  experience 
has  found  satisfactory  for  this  service.  A  second  method  is  to 
work  from  the  other  extreme,  basing  the  calculations  on  the 

177 


illumination  desired,  i.e.,  the  flux  of  light  method.     The  values 
recommended  for  this  are  shown  in  Table  3. 

In  either  method  there  are  several  general  points  to  be  re- 
membered. A  dark  object  is  always  an  extremely  difficult  sub- 
ject to  illuminate  regardless  of  the  quantity  of  light  provided. 
Table  3  shows  light  yellow  or  buff  objects  require  double 
the  illumination  necessary  for  white  surfaces,  while  a  medium 
buff  requires  three  times  as  much.  An  equally  important  con- 
sideration is  the  brightness  of  the  surroundings.  A  building  in 
a  poorly  lighted  section  would  require  only  a  fraction  of  the 
wattage  per  square  foot  to  produce  the  same  effect  as  an  installa- 
tion in  the  midst  of  brightly  lighted  surroundings. 
Problem  No.  1 

Let  us  assume  that  a  factory  yard  is  to  be  flood  lighted  to 
permit  work  to  be  done  at  night.  If  the  yard  is  175  feet  by  320 
feet  we  would  have  an  area  of  56,000  sq.  ft.  to  light.  From  table 
2  we  see  that  0.05  to  0.25  watts  per  sq.  ft.  are  required.  Assum- 
ing moderate  activity  and  allowing  for  ordinary  accident  hazard 
a  figure  of  0.10  could  be  taken.  Then  56,000  X  0.10  gives  5,600 
watts  required.  The  number  of  projectors  required  depends 
upon  local  conditions  and  can  be  determined  from  Table  1. 
If  neighboring  buildings  permit  the  equipment  to  be  mounted 
relatively  high,  12  units  of  the  500  watt  size  would  be  sufficient. 


One  of   the  Batteries   of    500-watt   projectors   that   floodlight  the 
Wrigley   Building 

1/8 


The  Wrigley  Building,  Chicago— An  excellent  example  of 

floodlighting  employing  198  500-watt  and  16  250- watt 

projectors 


Problem  No.  2 

Calculations  for  the  size  and  number  of  flood-lighting  units 
required  can  be  made  much  more  accurately  in  essentially  the 
same  way  as  for  interior  lighting.  The  first  step  is  to  multiply 
the  area  in  square  feet  of  the  surface  to  be  illuminated  by  the 
foot-candles  illumination  decided  upon.  The  product  is  the  total 
lumens  which  must  be  delivered  to  the  surface.  This  value  is 
then  increased  by  about  30  per  cent,  or  more,  to  provide  for 
depreciation  between  periods  of  cleaning  and  making  lamp  re- 
newals. The  result  obtained  is  the  number  of  lumens  which  must 
be  received  initially  upon  the  surface. 

The  next  step  is  to  refer  to  Table  1  and  with  the  location 
of  the  units  with  respect  to  the  surface  in  mind,  estimate  what 
percentage  of  the  total  light  projected  by  the  units  will  actually 

179 


strike  the  area  to  be  illuminated.  Dividing  the  percentage,  ex- 
pressed as  a  decimal,  into  the  lumens  required  initially  upon  the 
surface  itself  as  determined  above,  gives  the  total  number  of 
lumens  which  must  be  supplied  in  the  projected  beams. 

As  has  been  stated,  flood-lighting  projectors  of  medium  and 
wide  beam  are  available  in  which  from  40  to  50  per  cent  of  the 
light  of  the  lamp  is  directed  into  the  beam.  The  actual  values 
for  the  equipments  under  consideration  should  be  obtained'  from 
the  manufacturer.  Dividing  this  value  (as  a  decimal)  into  the 
total  lumens  required  in  the  projected  beams,  as  determined 
above,  gives  the  total  lamp  lumens  required  for  the  installation. 

The  lumen  outputs  of  the  lamp  ordinarily  used  in  flood  light- 
ing are  listed  in  Table  4.  The  total  lamp  lumens  required  divided 
by  the  lumen  output  of  the  size  of  lamp  used  gives  the  number 
of  projectors  required  for  the  installation. 

Suppose,  for  example,  it  is  desired  to  flood-light  the  front  of 
a  bank  building  from  a  distance.  The  surface  is  75  feet  high 
and  60  feet  wide  and  is  of  white  terra  cotta.  It  is  located  amid 
dark  surroundings. 

Area  to  be  lighted :  75  x  60  =  4500  sq.  ft. 
From  Table  3  it  is  decided  that  4  foot-candles  will  give  effective 

results ;  4500  x  4  =  18,000  lumens. 

This  value  is  increased  by  30  per  cent  to  provide  for  depreciation ; 
18,000  x  1.3  =,  23,400  lumens. 

From  a  consideration  of  the  location  of  the  units  and  their  beam 
characteristics,  it  is  estimated,  by  reference  to  Table  1,  that 
90  per  cent  of  the  light  in  the  projected  beams  will  strike  the 
surface ;  23,400  divided  by  0.9  =  26,000  lumens  necessary  in 
the  beams. 

The  manufacturer's  data  shows  that  the  equipment  it  is  desired 
to  use  directs  45  per  cent  of  the  lamp  lumens  into  the  beam ; 
26,000  divided  by  0.45  =  57,800  lamp  lumens  required,  with 
no  allowance  for  absorption  of  the  clear  glass  cover  plate. 

Assuming  that  a  further  allowance  of  approximately  15  per  cent 
must  be  made  for  absorption  of  the  clear  glass  cover  plate, 
multiplying  57,800  x  1.15  =.  66,500  total  lamp  lumens  re- 
quired. 

If  it  is  desired  to  use  the  500-watt  flood-lighting  lamp,  the  lumen 
output  is  found  from  Table  4  to  be  8100  lumens;  66,500 
divided  by  8100  =  8.2  (or  9)  units  required. 


Pennsylvania  Freight  Yards,   Chicago — Two-pole  tower 

mounting  eight    1000-watt   Floodlight    Units.     Two 

such  towers  are  employed  3000  feet  apart,  with 

beams  opposed. 


Pennsylvania  Freight  Yards,  Chicago — Lighted  by  two  banks  of 

eight  1000-watt  floodlighting  units,  mounted  on  towers  75  feet 

above  the  tracks.     The  two  towers   on  which  they  are 

mounted  are  3000  feet  apart  with  beams  opposed 

181 


PART  XII 
LIGHTING  FOR  OUTDOOR  SPORTS 

Tennis  Court  Lighting 

The  conditions  to  be  met  in  the  lighting  of  outdoor  courts 
present  problems  not  encountered  in  other  fields  of  illumina- 
tion. In  the  office,  for  instance,  the  desk  level  is  usually  as- 
sumed to  be  the  working  plane  and  all  illumination  calculations 
may  be  made  with  this  plane  as  the  basis.  In  the  case  of  the 
tennis  court,  however,  this  condition  is  materially  changed. 
There  is  no  fixed  plane  and  the  light  must  be  distributed  in 
such  a  manner  that  the  ball  is  well  lighted  during  its  entire 
travel.  . 


'6 


-6 


/5  - 


n 

/ 

'—  —       °- 

/ 

• 

\  ?i 

/< 

9' 

\ 

ill 

ELEVAT/ON 

Fig.   I 

The  Arrangement  of  soo-watt  MAZDA  C  Lamps  with  Angle  Type 

Enameled  Steel  Reflectors  in  the  Side  Lighting  System 

for  Tennis  Courts 

In  the  side  lighting  system,  as  the  name  implies,  units  are 
hung  at  a  moderate  height  along  the  sides  of  the  court,  while 
in  the  overhead  system  they  are  placed  far  above  the  ground 
over  the  center  line  of  the  court.  These  two  systems  are  the 
result  of  considerable  experimentation,  and  have  been  found 
very  satisfactory  in  service,  as  is  evidenced  by  the  number  of 

182 


courts    throughout    the    United    States    and    foreign    countries 
which  use  these  form's  of  lighting. 

The  United   States   National    Lawn  Tennis   Association   en- 


Effect  of  Lighting  as  Shown  in   Fig.   I   on   Preceding  Page 

dorses  night  tennis  when  the  installation  is  properly  laid  out 
to  obtain  the  desired  playing  conditions.  The  maintenance  of 
the  system  is  practically  nil,  save  for  an  occasional  cleaning  of 
lamps  and  reflectors. 

Night  playing  overcomes  the  limitations  of  daylight  and 
makes  one  court  do  the  work  of  two.  Any  man  who  cannot 
stand  the  heat  of  the  day  for  such  a  strenuous  game  as  tennis, 
enjoys  night  playing  in  the  open.  Lighted  courts  are  an  added 
attraction — a  valuable  asset  to  any  club  in  interesting  pros- 
pective members.  It  proves  as  interesting  for  spectators  as 
daytime  playing.  It  enables  the  busy  man  to  get  more  practice 
during  the  week  so  that  he  will  be  in  better  form  for  week-end 
matches. 

The  side  lighting  system  is  shown  in  plan  and  elevation  in 
Fig.  i.  It  calls  for  twelve  units,  six  on  each  side  of  the  court, 
spaced  and  hung  as  shown.  5OO-watt  M,azda  C  lamps  are  used 
with  suitable  angle  type  porcelain  enameled  reflectors  and 
weatherproof  holders. 

Some  of  the  courts  are  surrounded  by  netting,  the  support- 
ing structure  of  which  is  of  sufficient  strength  to  allow  mounting 
the  units  from  brackets  attached  thereto.  Under  other  condi- 
tions, it  is  advisable  to  suspend  the  lighting  units  from  cables 
stretched  between  posts  or  poles.  Three  of  these  on  each  side 
are  desirable. 

183' 


The  supporting  cable  should  consist  of  ^-inch  galvanized 
stranded  steel  wire.  The  lamps  and  reflectors  may  be  attached 
to  this  by  any  suitable  hanger. 

List  of  Material  Needed  for  Side  Lighting  System 

Amount 
Necessary 

5oo-watt   MAZDA  C  lamps 12 

Porcelain  enameled  steel  45-degree  angle  reflectors 12 

Holders    12 

Hangers     12 

25-ft.  wooden  poles   6 

<HHn.  galvanized  stranded  steel  wire 350  ft. 

No.   12  galvanized  iron  wire    . .  . 250  ft. 

No.  8  weatherproof  copper  w-re 600  ft. 

No.  14  weatherproof  copper  wire 75  ft. 

Double-pole,  single-throw,  6o-amp.  switch I 

Weatherproof  service  box    I 

Cross  arms  with  pins,  insulators,  lag  screws  and  braces 8 

Guy  anchors  with  turn  and  clamps   4 

The  overhead  lighting  system  in  plan  and  elevation  is  shown 
in  Fig.  2.  This  system  calls  for  four  i,ooo-watt  Mazda  C 
lamps  equipped  with  deep  bowl  enameled  steel  reflectors  and 
special  skirt  with  weatherproof  socket  holders.  They  should 
be  placed  as  indicated  in  the  dimensioned  drawing.  The 
fixtures  should  be  suspended  from  galvanized  stranded  cable, 


ELEVAT/ON 

©  Location  of  1000-watt  MAZDA  C  Lamp.mth.Bowlrshaped  Enamel  Steel  Reflectors 
Fig.   2 

Location  of  looo-watt  Units  in  the  Overhead  System  for  Tennis  Courts 

184 


stretched  between  45  foot  posts.  The  hangers  may  be  the  same 
as  those  used  for  the  side  lighting  system,  or  preferably 
automatic  cut-out  hangers  which  make  it  possible  to  lower  the 
units  for  replacement  of  lamps. 

List  of  Material  Needed  for  Overhead  System 

Amount 
Necessary 

looo-watt  MAZDA  C  Lamps   4 

Porcelain-enameled  steel  deep  bowl  reflectors 4 

Skirts 4 

Holders    4 

Hangers   .'...:..  — 4 

45  ft.  wooden  poles  ... 2 

%  in.  guy  and  messenger  cable 450  ft. 

No.  8  weatherproof  copper  wire 325  ft. 

No.  14  wieatherproof  copper  wire 25  ft. 

Double-pole,  single-throw,  6o-amp.  switch i 

Weatherproof  service  box i 

Guy  clamps    10 

Anchors  2 

Strain  insulators  2 

Cross  arms  with  pins,  insulators,  lag  screws  and  braces.  ..         2 

Clock  and  Court  Golf  Lighting 

Although  not  as  exacting,  the  conditions  to  be  met  in  this 
class  of  lighting  are  similar  to  those  of  the  tennis  court. 

There  must  be  sufficient  light  to  enable  the  player  to  follow 
the  ball  after  the  stroke  and  to  make  out  easily  the  outline  of 
the  hole  on  the  putting  green.  The  illumination  should  be  fairly 
even  in  order  that  one  will  not  be  misled  in  judging  distances 
and  in  sizing  up  any  irregularities  on  the  green.  The  distribu- 
tion of  light  from  the  lighting  units  should  be  wide  so  that  one 
may  find  the  ball  in  case  it  is  driven  off  the  fair  green. 

The  lighting  accessories  must  be  so  located  as  not  to  inter- 
fere in  any  way  with  the  play. 

By  artificially  lighting  a  clock  and  court  golf  course  the 
ardent  golfer  need  not  confine  his  activities  entirely  to  the  day- 
time. Hie  is  enabled  to  extend  his  practice  in  approaching  and 
putting  during  the  evening  hours,  thus  enabling  him  to  devote 
his  day's  playing  to  the  game  proper. 

Each  particular  court  is,  to  a  certain  extent,  a  problem  in  it- 
self and  thus  requires  special  attention.  One  club  met  the 
lighting  requirements  by  using  units  suspended  from  cross  arms 
attached  to  iron  poles  embedded  in  concrete.  The  spread  of  the 
cross  arms  is  eighteen  feet  and  the  units  are  fourteen  feet  above 
the  ground,  six  75o-watt  Mazda  C  lamps  are  used  equipped  with 
steel  reflectors. 

185 


Night  View  of  Sheepshead   Bay  Speedway   Taken   from   End  of   Grand- 
stand.   The   Illumination  of  the  Track  and  Field  is   accomplished 
by  MAZDA  C  Flood-lighting  Lamps  in  Form  L-l   Projectors 

The  Lighting  of  Motorcycle  and  Bicycle  Racing 

Motorcycle  and  bicycle  racing  have  become  so  popular  in  the 
past  few  years  that  many  races  are  held  at  night.  This,  of 
course,  means  that  artificial  light  must  be  provided. 

Racing,  especially  with  motorcycles,  has  a  certain  element 
of  danger  even  under  the  best  conditions.  Unless  the  track 
is  properly  lighted  this  danger  will  be  greatly  increased. 

The  scheme  outlined  in  Fig.  3  meets  the  requirements  for 
this  class  of  service.  Medium-sized  Mazda  C  lamps  (300-  or 
5OO-watt)  should  be  used,  equipped  with  enameled  steel  angle 
reflectors  that  project  the  maximum  light  at  approximately 


Fig.  3 

Section   of   Mbtordrome    Showing   Location   of   Units    for 
Lighting  Track  and  Seats 

forty-five  degrees  from  the  vertical.    The  units  should  be  so  lo- 
cated as  to  project  the  maximum  light  a  little  above  the  central 

186 


portion  of  the  track.  Where  it  is  necessary  to  locate  the  units 
above  the  lower  portion  of  the  track  they  should  be  suspended 
from  brackets  in  order  that  the  supporting  posts  may  be  re- 
moved several  feet  from  the  track  to  eliminate  danger.  The 
posts  should  be  spaced  approximately  every  twenty  feet.  The 
height  of  the  units  will  depend  on  the  contour  and  height  of 
the  track. 

This  system  has  the  following  advantages : 

A  number  of  small  units  produce  more  uniform  illumination 
than  fewer  large  units.  The  failure  of  one  unit  does  not  leave 
a  comparatively  large  section  of  the  track  in  darkness. 

The  light  is  absolutely  steady. 

There  is  no  glare  for  either  the  riders  or  spectators.  This 
feature  adds  to  the  safety  of  the  former  and  the  comfort  of  the 
latter. 

In  addition  to  the  units  required  for  the  track  proper,  there 
should  be  additional  low  wattage  lamps  at  the  back  of  the  spec- 
tators to  aid  in  finding  seats  and  reading  programs. 

The  Lighting  of  Outdoor  Arenas 

The  illumination  of  outdoor  areas  sufficiently  large  to  be 
used  for  auto  polo,  drilling,  foot-ball,  hockey,  skating,  play- 
grounds and  athletic  contests  in  general,  offers  exceptionally 
interesting  problems. 

Three  methods  of  illumination  are  employed  as  follows : 

(1)  Suspending   units   over   the   area   by   messenger   cable 
strung  between  poles.     The  units  must  be  hung  at  a  sufficient 
height  to  eliminate  any  danger  of  glare  to  either  the  observers 
or  players.     The  spacing  must  be   such   that   for  the  hanging 
height  and  type  of  reflector  employed  the  illumination  is  reason- 
ably uniform. 

(2)  Lighting   from   units   located   at   the   sides    employing 
standard   angle  type  reflectors.     These  rriust  be   suspended   at 
such  a  height  and  in  such  positions  as  to  prevent  the  possibility 
of  annoyance  to  the  players  and  to  observers  in  the  stand. 

(3)  The  employment  of  floodlighting  projectors  located  on 
the  roof  of  the  grandstand,  adjacent  buildings,  special  poles,  or 
even  trees. 

187 


Night  View  of  a  Drill  Field  Lighted  by  Nine  75o-watt  MAZDA  C  Lamps 
in  Angle  Steel  Reflectors  on  Poles  Around  the  Edge  of  the  Field 

Each  particular  system  has  certain  advantages.  The  one  to 
be  selected  will  depend  upon  the  area  to  be  lighted  and  local 
structural  conditions. 

If  the  field  is  comparatively  small  and  only  a  low  intensity 
is  required,  as  for  example,  a  small  drill  field,  skating  pond, 
or  playground,  poles  can  be  erected  without  difficulty.  The 
overhead  system  employing  medium  size  Mazda  C  lamps  with 
standard  distributing  reflectors  is  probably  the  most  simple  in- 
stallation. 

Where  there  is  a  grandstand  or  similar  structure  and  the 
area  to  be  lighted  is  comparatively  narrow,  angle  type  reflectors 
fitted  with  standard  Mazda  C  lamps  are  inexpensive  and  easily 
installed. 

For  lighting  areas  too  wide  to  permit  the  use  of  the  over- 
head system,  and  when  only  a  low  intensity  is  required,  angle 
type  units  located  on  poles  around  the  edge  of  the  field  prove 
satisfactory.  Tlhey  are  much  less  expensive  than  floodlighting 
equipment. 

Where  the  area  to  be  lighted  is  wide  and  a  relatively  high  in- 
tensity of  illumination  is  desirable,  floodlighting  equipments 
offer  the  best  means  of  solution.  The  type  of  floodlighting 
projector  employed  will  depend  on  the  available  means  of  sup- 
port and  the  distance  between  units. 

188 


The  following  table  gives  the  desirable  intensity  for  various 
outdoor  sports. 

Intensity  in         Watts  per 
Foot-candles     Square  Foot* 


Football    

2  0—6  0 

0  50—1  50 

Hockey    

4.0—6.0 

1.00—1  50 

Polo     ... 

2  0  —  4  0 

0  50—1  0 

Skating 

0  5—2  0 

0  10  0  50 

Playgrounds 

1.0—3.0 

0.25—0.75 

*  Based  on  use  of  high  power  MAZDA  C  lamps  and  efficient  reflectors. 

Lighting  of  Bathing  Beaches 

Bathing  beaches  have  always  been  a  popular  place  of  as- 
sembly at  night.  This  is  the  only  time  when  a  large  majority 
ol  the  people  can  enjoy  them.  The  pleasure  of  bathing,  how- 
ever, is  usually  denied  because  of  the  danger  of  being  lost  in 
the  darkness. 

It  is  a  relatively  simple  matter  to  light  the  beach  so  that 
it  is  safe  for  night  bathing.  Artificial  illumination  of  the  bath- 
ing beach  will  materially  increase  its  patronage,  and  prove  a 
boon  to  the  working  class. 

The  nature  of  the  average  beach  is  such  that  the  lighting 
units  must  be  placed  a  considerable  distance  from  the  water 
and  for  this  reason  floodlighting  projectors  offer  the  best  solu- 
tion. They  should  be  placed  thirty  feet  or  more  above  the 
beach  and,  when  possible,  located  in  two  banks  about  one 
hundred  feet  apart  so  as  to  provide  light  from  more  than  one 
direction.  Hotels  or  other  buildings  adjacent  to  the  beach 
usually  provide  convenient  means  of  mounting  the  projectors. 
From  y^  to  2  foot-candles  of  illumination  should  be  provided. 

The  Lighting  of  Trap  Shooting  Ranges 

As  difficult  as  the  problem  may  seem,  the  successful  lighting 
of  ranges  for  trap  shooting  is  an  established  fact.  In  a  recent 
day  and  night  meet  all  of  the  contestants  made  as  good  scores 
by  night  as  during  the  day,  while  some  made  better  scores. 
In  another  meet  held  in  the  middle  west,  one  of  the  entrants 
made  ninety-nine  hits  out  of  a  possible  one  hundred  under 
artificial  lighting. 

One  method  of  lighting  this  particular  sport  is  shown  in 
Fig.  4.  Four  projectors  are  used,  located  behind  the  shooter's 

189 


stand  or  handicap  positions  twenty  feet  above  the  ground.  Each 
of  the  projectors  is  equipped  with  a  i,ooo-watt  Mazda  C  lamp. 
The  lamps  should  be  focused  so  that  the  spread  of  the  light 
will  be  approximately  thirty  degrees.  After  installing  the  units 
they  should  be  pointed  in  the  direction  indicated  by  the  lines 
on  the  diagram  at  such  an  angle  vertically  that  the  illumination 
on  the  ground  at  the  limit  of  travel  of  the  clay  pigeons  will  be 
even.  Having  obtained  this  condition  each  projector  should  be 


Fig.  4 
Method  of  Lighting  Trap  Shooting  Ranges  in  Plan  and  Elevation 


pointed  upward  the  same  amount  until  the  lower  edge  of  the 
'!,eam    of    light    is    approximately    as    shown    in    the    elevation, 

(Fig.  4). 

This  method  has  the  advantage  of  simplicity  of  installation 
and  operation.  Tfhere  is  sufficient  direct  light  from  the  units 
to  illuminate  the  shooter's  stand.  The  light  covers  the  entire 
area  over  which  the  pigeons  will  be  thrown  with  sufficient  in- 
tensity to  make  them  very  conspicuous.  The  cost  of  operation 
is  low.  The  energy  required  is  4,000  watts  which  at  ten  cents 
per  kilowatt  hour  will  cost  forty  cents  for  each  hour. 

190 


PART  XIII 
LIGHTING  FOR  INDOOR  RECREATIONS 

Pool  and  Billiard  Parlors 

When  considering  the  lighting  requirements  for  pool  and 
billiard  tables,  two  important  points  must  receive  careful  at- 
tention. These  are  a  high  intensity  and  extremely  good  diffu- 
sion. The  necessity  for  these  is  easily  seen  from  the  fact  that  the 
playing  area  is  rather  small  and  distances  and  angles  must  be 


L  I 


1 

1 

i 

cr 

1 


. 
3 


n2 

w- 
n 

^n2'0^ 

. 

4-0 
O    .  O 


a  'b  c 

FIG    1 

THREE  COMMON  METHODS  OF  LIGHTING  BILLIARD  TABLES 

a  =  3-75  or  100  watt  bowl  enameled  Mazda     C     lamps  in  heavy  density  glass 

.  intensive  type  bowl  reflectors. 

b  ==.  4-50.  or  75  watt  diffusing  bulb  Mazda  lamps  in  heavy  density  glass  in- 
tensive type  bowl   reflectors. 

c  =  2-100   or    150  watt  bowl   enameled   Mazda     C     lamps    in   heavy  density 
glass  intensive  type  bowl  reflectors. 

carefully  gauged.  A  shadow  cast  by  a  ball  is  very  apt  to  mis- 
lead players  in  gauging  distances,  or  otherwise  disconcert  them 
causing  them  to  fumble  the  shot.  No  shadows  cast  by  players 
standing  in  the  immediate  vicinity  of  the  table  should  be  al- 
lowed to  fall  on  the  table,  unless  these  shadows  are  so  soft 
as  to  be  imperceptible. 

There  are  three  methods  by  means  of  which  these  require- 
ments can  be  met  in  a  satisfactory  manner : 


191 


A — Individual  units  located  over  each  table  supplemented  by 
a  low  intensity  of  general  illumination. 

B — Translucent  reflectors  placed  over  each  table  which  serve 
both  as  local  light  for  each  table  and  general  lighting  for  the 
entire  room. 

C — Straight  general  system  employing  semi-indirect,  indirect 
or  enclosing  diffusing  units. 

Individual  lighting  of  tables  is  by  far  the  most  common. 
This  is  due  no  doubt  to  the  fact  that  the  grouping  of  low  watt- 
age lamps  over  tables  in  order  to  secure  a  desirable  intensity 
was  inaugurated  before  the  advent  of  high  wattage  lamps.  It 
is  customary  with  this  type  of  installation  to  use  opaque  deep 
bowl  reflectors  mounted  approximately  four  or  five  feet  above 
the  table.  Metal  reflectors  are  best  suited  because  no  light  is 
transmitted  through  them,  with  the  result  that  little  direct 
light  reaches  the  eye. 

With  such  a  system,  it  is  necessary  to  use  some  means  of 
general  illumination,  as  otherwise  the  room  will  be  very  gloomy 
and  cheerless.  Unless  care  is  exercised  in  designing  the  in- 
stallation and  choosing  the  fixtures,  the  lighting  system  is  apt 
to  be  unsightly. 

The  units  should  be  hung  high  enough  so  that  they  do  not 
interfere  with  a  player's  movements,  and  are  not  likely  to  be 
struck  with  a  cue.  It  is  necessary  for  the  reflectors  to  be  of 
such  type  that  the  angle  of  cut-off  light  from  the  lamp  is  fairly 
sharp  and  no  direct  light  is  permitted  to  enter  the  player's  eyes. 
As  stated  before,  a  medium  intensity  of  general  illumination  is 
necessary  with  such  a  system  and  this  can  best  be  obtained  by 
using  100  or  200- watt  MADZA  C  lamps  in  indirect,  semi-indirect, 
or  enclosing  units,  spaced  to  provide  from  one-quarter  to  one- 
half  watt  per  square  foot  of  floor  area. 

With  the  indirect  system,  because  of  the  diffusely  reflected 
light  from  the  ceiling  and  walls,  the  placement  of  tables  with 
regard  to  the  lighting  units  is  not  important. 

The  semi-indirect  system  requires  more  careful  placing  of 
units  with  respect  to  tables  in  order  to  keep  shadows  short  and 
soft.  Best  results  are  obtained  with  this  system  when  a  group  of 
tables  are  to  be  lighted,  as  the  units  can  then  be  so  placed  as 

192 


-w-  -  .  -  -r 

i 

VCOUNTER. 
] 

f 

]pQ-| 

]f 

J  

-4-- 

« 

H 

f[ 

•1  1  1  l» 

D"   • 

i 

4 

B 

W 

1 

H  1 

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i 

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» 

Q                         /^COUNTER" 

Fig.   2 

',  PLAN  OF  BILLIARD  ROOM   LIGHTING  INSTALLATION 
XX «  300  wall  Mazda  "C"  lamp  in  enclosing  glassware 

to  make  tables  receive  predominating  light  from  several  di- 
rections. 

While  enclosing  units  diffuse  the  light  to  a  certain  extent, 
still  most  of  the  light  received  under  such  a  system  is  direct 
light,  and  hence  particular  care  must  be  used  in  placing  the 
units  so  that  objectionable  shadows  will  not  interfere  with  the 
player's  aim.  Fig.  2  shows  a  method  of  locating  units  in  order 
to  obtain  the  desirable  effect. 

With  totally  indirect  lighting,  and  with  light  surroundings, 
fromf  2.0  to  3."  watts  per  square  foot  should  be  provided ;  with 
enclosing  units  from  1.5  to  2.0  watts  per  square  foot  are  de- 
sirable ;  the  value  for  semi-indirect  lighting  falling  betwleen  these 
two  and  being  dependent  of  the  type  of  unit  and  room  finish. 

Bowling  Alleys 

The  very  nature  of  bowling  is  such  that  unless  careful  con- 
sideration is  given  to  the  proper  shielding  of  light  sources,  it 
is  very  likely  that  the  pastime  cannot  be  carried  on  with  any 
degree  of  enjoyment.  Bowling  alleys,  by  virtue  of  their  con- 
struction, are  long,  narrow  areas  with  comparatively  low  ceilings, 
which  practically  limit  the  spacing  of  outlets  to  the  region 
above  the  alleys  themselves,  where  the  lighting  units  are  most 
conspicuous.  It  is  obvious  that  unless  they  are  properly  shielded 
the  resulting  glare  may  be  such  as  to  render  the  player  unable 
to  aim  his  ball  effectively. 

193 


The  intensity  on  the  alley  itself  should  be  fairly  high,  while 
at  the  end,  on  the  pins,  the  intensity  should  be  approximately 
double  that  on  the  alley.  Deep  bowl  reflectors  with  75- 
watt  Mazda  lamps  are  often  placed  in  a  single,  line  down  the 
clley.  In  some  cases  the  spacing  between  units  is  too  great 


U 


CONDUIT  OR  SOME 
SIMILAR.  RIGID 
SUPPORT 


T-  -t~ 

ry  j      j 

1      1       1       1      1       1      l 

i     i     i     i     i     1     i 

J63'-0"  \ 1 1 -I—  15-0" 


H 1 1 1 1 \  63-0 

^f^F^F^'r 7l6"T  ^'T^T^vT1'6^  RUNWAV  i 


Fig.  3 

STANDARD  METHOD  OF  BOWLING  ALLEY  LIGHTING 
4-*  75  wall  Mazda  C  lamp  m  angle  steel  reflector 

and  the  resultant  illumination  very  uneven,  creating  light  and 
dark  areas  or  striated  effect,  which  proves  very  annoying.  Then 
again,  with  an  installation  using  deep  bowl  reflectors,  the  re- 
flected glare  from  the  polished  floor  surfaces  is  likely  to  prove 
Lroublesomie. 

The  best  method  of  obtaining  an  evenly  distributed  light  on 
the  surface  of  the  bowling  alley  and  a  high  intensity  on  the 
pins,  free  from  glare  or  glaring  reflections,  is  to  utilize  75-watt 
Mazda  lamps  in  angle  reflectors  mounted  in  a  single  line  over 
the  center  of  the  alley,  as  shown  in  Fig.  3. 

When  using  this  system,  which  is  rapidly  becoming  standard, 
.i  is  necessary  to  use  conduit  or  some  similar  rigid  support  for 
;:he  units,  as  otherwise  they  are  likely  to  twist  or  turn,  thus 
cither  throwing  the  light  on  a  neighboring  alley  or  else  in  the 
player's  eye. 

This  system  can  be  used  for  lighting  two  alleys,  and  when 
so  employed,  outlets  for  75  or  100-watt  MAZDA  lamps  with  the 
proper  size  angle  reflectors  should  be  spaced  in  a  single  line, 
midway  between  the  two  alleys,  with  individual  units  on  each 
alley  at  the  pins. 
Indoor  Tennis  Courts 

Indoor  tennis  is  popular  among  those  adherents  of  the  game, 
as  it  is  free  from  the  vagaries  of  the  weather  and  differences 
in  seasons.  The  entire  area  housed  by  the  structure  should  be 

194 


lighted  to  a  fairly  high  intensity,  and  not  only  must  the  flooi 
surface  be  lighted,  but  the  units  must  be  hung  sufficiently  high 
to  enable  a  ball,  traveling  20  feet  in  the  air,  to  be  clearly  visible 
at  all  times.  If  the  intensity  is  markedly  uneven  over  the 
court,  light  and  dark  patches  will  be  present  and  the  ball  in 
traveling  from  a  lighter  to  a  darker  area  will  appear  to  slow 
down;  conversely,  when  traveling  from  a  darkened  area  to 
:i  lighter  area,  it  will  appear  to  gather  speed.  This  apparent 
variation  in  the  ball  speed  may  render  the  player  unable  to 
gauge  properly  the  speed  of  the  ball  in  order  to  make  a  return. 
With  constant  repetition,  this  will  defeat  the  primary  purpose 
of  the  lighting  installation,  which  is  to  enable  the  gam\e  to  be 
played  as  effectively  at  night  as  during  the  day.  Glaring  light 
sources  will  render  the  players  more  or  less  ineffective  in  making 
returns. 

All  three  of  the  general  systems  of  lighting  are  applicable  to 
this  problem.  The  direct  system  is  the  most  efficient,  but,  if 
it  is  not  carefully  designed,  the  installation  may  easily  become 
glaring.  The  semi-indirect  system  can  be  applied  where  the 


c. 
W       H 

3 
} 

1Q-  0" 

a                       x 

fcU            lA-n"              •» 

(                              X. 

tt 

»< 

5 

11 

3 

3 

r> 

1 

V 

« 

i                             W 

S 

Fig.  4 

PLAN  OF  TENNIS  COURT  SHOWING  LOCATION  OF  LIGHTING  UNITS 

&=500  wall  Mazda  C  lamp  in  semi-iadirepi  or  enclosinq 
diffusing  .globe 

NOTE:  Minimum  Hanging  Height  SO  feet 

wall  and  ceiling  finish  of  the  building  is  comparatively  light 
in  color,  thus  permitting  a  good  portion  of  the  light  to  be  re- 
flected from  these  surfaces.  The  totally  indirect  system  can 
be  applied  only  where  the  wall  and  ceiling  finish  is  such  as  to 


have  a  high  coefficient  of  reflection.  This  system  gives  the 
best  diffusion  with  little  or  no  likelihood  of  glare,  but  since  all 
of  the  light  must  be  reflected  from  the  ceiling,  it  requires  approxi- 
mately double  the  wattage  required  for  a  direct  lighting  system. 

For  all  practical  purposes,  enclosing  or  semi-enclosing  dif- 
fusing units  are  to  be  recommended,  where  the  ceiling  height 
is  25  feet  or  more.  High  wattage  Mazda  C  lamps  placed  on 
wide  centers  are  preferable  to  low  wattage  lamps  more  closely 
spaced,  as  there  is  less  likelihood  of  several  units  being  in  the 
field  of  view.  Light  colored  walls  and  ceilings  will  eliminate 
any  difficulty  with  uneven  lighting. 
Squaslh  Courts 

The  principal  requirements  for  lighting  a  squash  court  are 
a  high  intensity,  good  diffusion  and  absence  of  glare.  The 
game  of  squash  calls  for  rapid  play  with  close  attention,  inas- 
much as  the  movements  of  a  small  ball  must  be  closely  followed. 

The  room  in  which  this  game  is  played  varies  from  50  to 
30  in  length,  and  from  20  to  15  feet  in  width.  The  walls  and 
floor  are  hard  and  smooth.  There  are  usually  two  finishes  ap- 
plied to  the  walls  and  ceiling.  In  som.e  cases  a  dark  finish,  such 
as  mahogany,  is  used  in  conjunction  with  a  white  ball,  so  as  to 
get  the  proper  contrast  between  the  ball  and  walls. 

In  other  cases,  particularly  in  England,  the  walls  are  painted 
a  flat  white  and  a  black  ball  is  used.  It  is  evident  from  this 
that  the  dark  finished  court  makes  the  greatest  demand  on  the 
lighting  installation  inasmuch  as  it  posseses  a  very  low'  reflec- 
tion factor. 

Occasionally  the  construction  of  the  ceilings  of  these  courts 
is  such  as  to  permit  the  hanging  of  deep  bowl  direct  lighting 
units,  so  as  to  conceal  them  from  view,  save  when  looking  di- 
rectly upwards.  That  is,  they  can  be  hung  along  side  of  drop 
beams.  In  other  cases,  it  is  possible  to  set  these  so  that  the 
mouth  of  the  reflector  is  flush  with  the  ceiling  and  provide  a 
plight  metal  shield  on  the  side  generally  faced  by  the  players. 
Angle  reflectors  are  scarcely  suitable,  for  the  play  is  likely  to 
progress  on  all  sides  and  unsymmetrical  distribution  of  light  is 
not  effective. 

Where  the  fixture  moist  be  in  full  view,  semi-enclosing  units 
r,f  the  diffusive  and  decorative  type  find  use.  The  precaution 
must  always  be  taken  of  carefully  guarding  the  glassware  from 
balls  struck  upwards.  As  mentioned,  the  power  required  prop- 

196 


crly  to  light  the  court  will  vary  with  the  room  finish.  From 
three  to  four  watts  per  square  foot  with  the  deep  bowl  diiect 
lighting  installation,  in  a  darkly  finished  room,  will  prove  satis- 
factory, while  with  the  enclosing  units,  under  the  same  con- 
ditions, upwards  of  five  watts  per  square  foot  is  necessary.  With 
b'ght  surroundings  the  values  can  be  greatly  decreased. 

Skating  Rinks 

Of  all  indoor  recreations  that  of  ice  skating  meets  with  most 
popular  favor.  This  is  so  because  the  sport  is  not  limited  to  a 
small  number  of  people  and  there  is  practically  no  age  barrier. 

The  pleasure  afforded  is  nearly  equivalent  to  that  of  outdoor 
skating  and  in  many  ways  indoor  ice  skating  is  more  to  be  pre- 


h— 18'-0H--K-18'-0"-H 

RinK 


n 


Office 
Offu:e 


Fig.  5 

PLAN  OF  ICE   SKATING  RINK 

XX »  300  wall  Mazda  "C"  lamp  in  semi-indirect  unit 
®  =  75  wall  Mazda  "C1  lamp  in  semi-mdirecl  unil 
3=3-35  wall  Mazda'S"  lamps,  wall-bracKel 

ferred  inasmuch  as  its  enjoyment  is  not  dependent  on  weatrier 
conditions. 

When  considering  the  lighting  of  skating  rinks,  two  types 
.  ome  to  mind — one,  purely  utilitarian,  non-decorative,  for  use 
in  such  rinks  as  are  devoted  mczlly  to  hockey  playing  and  simi- 
lar contests ;  the  other  less  efficient,  more  decorative,  harmoniz- 
ing and  blending  with  the  finish  and  appointment  of  the  rink. 
In  the  first  type,  as  stated  before,  the  primary  consideration 
:'s  adequate  diffusion.  In  a  hockey  game  the  shadows  cast  by 
the  players,  either  when  separated  or  in  a  scrimmage,  must 


197 


not  be  dense  enough  to  cause  the  players  to  lose  track  of  the 
hockey  puck. 

If  direct  lighting  is  to  be  employed,  it  is  necessary  to  space 
outlets  quite  closely  together  to  eliminate  any  shadow  diffi- 
culties. In  choosing  the  type  of  reflector,  we  must  consider 
the  question  of  efficiency,  appearance,  and  cost.  Bowl  enameled 
Mazda  C  lamps  in  RLM  Standard  Dome  reflectors  or  clear 
Mazda  lamps  in  deep  bowl  mirrored  glass  reflectors  represent 
one  extreme,  diffuse  enclosing  units  the  other.  A  practice  which 
has  much  in  its  favor  is  the  use  of  dense  opal  deep  bowl  re- 
flectors, transmitting  some  light  to  the  ceiling,  permitting  a 
fairly  ornamental  appearance,  and  yet  relatively  effective  in 
redirection  of  light. 

The  size  01  lamp  to  be  used  will  vary  somewhat  with  the 
ceiling  height.  For  ceiling  heights  of  20  feet  or  under,  100-watt 
Mazda  C  lamps,  heavy  density  opal  glass  reflectors,  spaced  ap- 
proximately on  10  by  10  foot  centers,  will  provide  a  good  in- 
tensity on  the  rink,  together  with  a  high  degree  of  diffusion. 
Where  the  ceiling  height  ranges  between  20  and  30  feet,  2OO-watt 
bowl  enameled  Mazda  C  lamps  in  the  same  type  of  reflector 
spaced  on  15  by  15  foot  centers  will  provide  approximately  the 
same  intensity. 

Where  rinks  are  employed  purely  for  general  skating  pur- 
poses in  large  cities,  they  should  be  well  appointed  and  critical 
attention  given  to  their  interior  finish.  The  lighting  of  these 
rinks  rmust  necessarily  be  of  a  more  ornamental  character  in 
order  to  harmonize  with  the  surroundings.  The  intensity  here 
need  not  be  so  high  as  that  required  on  rinks  devoted  to  skating 
'  ontests.  Diffusion,  however,  must  be  of  a  fairly  high  degree 
inasmuch  as  exhibition  matches  are  sometimes  staged  which 
necessitate  comparative  freedom  from  dense  shadows. 

The  two  systems  which  work  out  best  for  this  service  and 
are  commonly  employed,  are  the  semi-indirect  and  enclosing 
unit  systems.  The  diffusion  under  each  is  very  good,  and  a 
fairly  high  intensity  can  be  obtained  at  a  reasonable  consump- 
tion of  power. 


198 


PART  XIV 

MAINTENANCE  OF  INTERIOR  LIGHTING 
SYSTEMS 

To  account  for  the  poor  attention  which  lighting  systems 
as  a  whole  receive,  it  is  necessary  to  believe  that  most  persons 
fail  to  realize  with  what  rapidity  or  to  what  extent  dust  and 
dirt  cut  down  the  effectiveness  of  a  lighting  system;  or  that, 
knowing  the  extent  of  the  depreciation,  they  undervalue  the 
l:'ght  allowed  to  go  to  waste;  or  that,  with  the  value  of  the 
wasted  light  knowin,  they  believe  a  maintenance  system  to  be 
difficult  and  costly  to  operate. 
Extent  of  Lighting  Depreciation 

In  calculating  the  wattage  for  a  modern  lighting  system,  the 
illuminating  engineer  uses  a  "depreciation  factor"  to  compensate 
ior  normal  average  depreciation  in  service.  Good  practice  calls 
for  an  allowance  of  30  per  cent  more  light  initially  than  is  ex- 
pected in  service  in  fairly  clean  locations  and  fairly  clean  opera- 
tions (23  per  cent  loss)  ;  in  dirty  locations  and  dirty  operations 
50  per  cent  or  even  ico  per  cent  is  really  necessary  (33^  or  50 
per  cent  loss).  These  figures  doubtless  seem  high  but  the  illu- 
minating engineer  uses  them  with  the  knowledge  gained  from 
experience  that  unless  the  maintenance  of  the  system  is  handled 
in  better  fashion  than  is  usually  the  case,  the  system!  will  in  a 
short  time  be  giving  less  light  than  it  was  designed  to  furnish. 

There  are  six  principal  causes  of  lighting  depreciation.  These 
lire:  (i)  dirty  reflectors  and  lamps;  (2)  darkened  walls  and  ceil- 
ings ;  (3)  depreciation  of  lamps ;  (4)  empty  sockets ;  (5)  unob- 
served burnouts;  (6)  improperly  made  replacements.  In  gen- 
eral, when  installed  in  relatively  favorable  locations,  open  re- 
flector units  snow  a  depreciation  in  total  light  output  of  from 
TO  to  25  per  cent  in  four  weeks'  time.  Where  excessive  smoke 
and  dust  are  the  rule,  the  depreciation  over  this  same  period  may 
be  as  high  as  40  per  cent.  The  effect  of  darkening  of  the  ceiling 
and  walls  due  to  smoke  and  dust  depends  upon  the  type  of  unit, 
the  location,  i.e.,  whether  clean  or  dirty,  and  the  original  color 
nnd  finish;  typical  data  are  given  in  Table  i.  MAZDA  C  lamps 
throughout  life  average  above  90  per  cent,  of  their  initial  output. 
Blackened  bulbs  are  continually  decreasing  in  number,  but  where 
inspection  shows  a  bulb  to  be  considerably  darkened  the  lamp 
should  be  replaced  with  a  new  one.  Empty  sockets  and  unob- 
served burnouts  in  indirect  and  multi-light  fixtures  are  fre- 

199 


TABLE  1— Effect  of  Darkening  of  Ceilings  and  Walls  on  Illumination  at  the  Work 


Ceiling: 

Very  Light 

Fairly  Light 

Fairly  Dark 

Walls: 

JFairly 
Light 

Fairly 
Dark 

Very 
Dark 

Fairly 
Light 

Fairlyl 
Dark 

Very 
Dark 

Fairly 
Dark 

Very 
Dark 

Type  of  Unit 

Foot-Candles  Illumination  in  Per  Cent 

-               RLM 
lfl|_       Standard 

JEMm        Dome 

100 

96 

92 

98 

94 

90 

94 

90 

«                Deep 
/Kk             Bowl, 
£tl            steei 

100 

96 

91 

98 

95 

91 

95 

91 

••—  ••           Semi- 
^-A           Enclosing 

100 

90 

80 

95 

85 

78 

83 

76 

/  t  \             Light 
V/       V         Density 
—        Semi-Indirect 

100 

87 

76 

82 

71 

63 

55 

50 

^fy           Indirect 

100 

90 

83 

73 

63 

57 

37 

33 

quently  found  when  complaints  of  inadequate  illumination  are 
investigated.  Replacement  of  burned  out  lamps  With  new  ones 
of  a  wrong  size  or  of  an  incorrect  voltage  rating  is  often  found 
to  be  the  cause  for  dissatisfaction  with  the  lighting. 


Fig.  i. — Loss  of  Light  When  Lamps  are  Operated  Undervoltage. 
The  data  are  for   no-volt  MAZDA  lamps 


200 


73  _ 

C 

o 


2.1  Foot-candles 
(As  found) 


3.1  Foot  -candles 

(After  washing) 


5.0  Foot  -candle* 
(  New  lamp  of  proper 
voltage) 


1.2  Foot -candles 

(Walls  and  ceiling 
reftnished) 


Fig.  2. — Effect   of   Proper   Maintenance   in   Building   up   the   Illumination 

from   a   Depreciated    Lighting   System.     The    data   were   obtained 

in    investigating   a   complaint    on   an    indirect    system 


When  one  considers  the  combined  effect  of  the  different 
causes  of  depreciation,  it  is  easy  to  understand  why  it  is  that  the 
illumination  at  the  work  will  often  be  reduced  very  seriously  in 
a  relatively  short  space  of  time.  The  reason  that  this  waste  goes 
unsuspected  is  twofold :  First,  because  depreciation  is  gradual 
and,  second,  because  the  eye  adjusts  itself  to  changes  in  illumi- 
nation automatically.  Changes  in  intensity  which  when  brought 
about  gradually  pass  unnoticed  by  the  eye  would  be  extremely 
annoying  if  made  so  rapidly  that  the  eye  did  not  have  time  to 
adjust  itself.  Usually  a  falling  off  of  illumination  is  not  apparent 
until  a  point  is  reached  where  complaints  begin  to  be  made  of 
inaccuracies  in  the  work  or  where  the  trouble  mlanifests  itself  in 
lowered  production. 

Even  then  inadequate  maintenance  is  rarely  suspected  as  the 
cause  for  the  dissatisfaction.  A  case  in  point  is  that  of  an  office 
lighting  installation  investigated  in  response  to  a  complaint.  A 
system  of  indirect  lighting  had  been  installed  two  and  one-half 
years  previously.  The  ceiling  had  been  painted  a  flat  white  and 
the  walls  finished  in  a  light  buff.  At  the  time  the  installation 
was  put  in,  the  illumination  was  adequate. 

Measurements  made  in  response  to  the  complaint  showed 
that  only  2.7  foot-candles  were  being  obtained  on  the  desk  tops. 
A  thorough  washing  of  the  lamps  and  reflectors  brought  the  il- 
lumination up  to  3.7  foot-candles — an  increase  of  more  than  35 

201 


Fig.  3 — The  Foot-candle  Meter  Measures  Light  at  the  Work  and  Reveals 
the  Combined  Effect  of  all  Possible  Causes  of  Depreciation 

per  cent — and  this  in  spite  of  the  fact  that  the  reflectors  had 
been  wiped  out  at  fairly  regular  intervals.  The  lamps  had  .been 
in  service  more  than  two  years  and  their  rating  was  several 
volts  higher  than  the  average  voltage  of  the  circuit.  New  lamps 
of  proper  rating  increased  the  illumination  to  over  5  foot-candles. 


MAINTENANCE     RECORD 


35V 


JANFEB 


12  IZ 


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Ilk  KM  HI-SUM 


t* 


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7.«7f7V75707o 


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JUN 


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if  (ri 


JUL 


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fjov  ocq 


Fig.  4. — Lighting   Maintenance   Record 
(From  I.E.S.  Transactions) 


202 


Refinishing  the  ceiling  and  walls  in  their  original  tones  brought 
the  illumination  up  to  slightly  nnore  than  7  foot-candles.  The 
effect  of  the  several  steps  in  the  restoration  process  which  in- 
creased the  illumination  from  2.7  to  more  than  7  foot-candles  is 
shown  graphically  in  Fig.  2.  Experience  indicates  that  in  gen- 
eral more  than  30  per  cent  of  the  light  which  is  paid  for  is  al- 
lowed needlessly  to  go  to  waste.  In  many  individual  cases  one- 
half  or  even  two-thirds  is  being  thrown  away  through  lack  of 
attention  to  simple  maintenance  requirements. 

Value  of  Light  Wasted 

If  the  value  of  the  light  needlessly  wasted  were  arrived  at 
simply  by  calculating  its  cost  in  ratio  to  the  total  cost  of  the 
lighting  system,  the  figures  might  seem  insignificant  in  relation 
to  the  total  operating  cost  of  an  office  or  of  a  factory  building; 
for  the  total  cost  of  the  light  is  itself  a  small  item  when  so  con- 
sidered. To  obtain  a  correct  valuation  it  is  necessary  to  con- 
sider to  how  great  an  extent  the  work  carried  on  is  dependent 
upon  artificial  illumination  and  to  what  degree  this  work  is  af- 
fected by  a  decrease  in  the  quantity  of  light. 

In  industrial  lighting  is  found  a  basis  upon  which  to  formiu- 
iate  an  idea  of  the  value  of  higher  levels  of  illumination.  For  a 
number  of  years  prior  to  the  war,  factories  had  been  getting 
along  on  just  slightly  more  than  enough  light  to  "see."  State 
Codes  to  establish  mandatory  minimum  values  of  illumination 
in  industry  were  being  talked  about  because  of  the  need  for  as- 
suring workmen  sufficient  light  for  safety.  That  light  in  quan- 
tities which  would  make  seeing  entirely  involuntary,  that  would 
greatly  minimize  accident  hazard,  and  that  would  make  surround- 
ings bright  and  cheerful,  might  be  employed  to  advantage  in 
industry  was  hardly  more  than  a  theory.  Since  that  time,  experi- 
ments* have  been  conducted  which  show  how  vision  is  improved 
by  increased  illumination  and  testsf  have  demonstrated  that 
startling  increases  in  production  have  accompanied  improve- 
ments in  the  artificial  lighting  systems  in  factories.  These  in- 
creases have  been  accomplished  at  an  additional  cost  on  the 
average  of  only  2  or  3  per  cent  of  the  payroll.  They  are  men- 


*Ferree  and  Rand,  Transactions  I.  E.  S.,  Vol.  XV,  No.  9,  p.  769. 

Ferree  and  Rand,    I.    E.    S.    Convention    Paper,   1921. 

Luckiesh-Taylor-Sinden,    Electrical   World,    Oct.    1,    1921,   p.    668. 
tDurgin,   Electrical  Review,   Mar.   22,   1919. 

Harrison-Haas-DopV~,   Electrical   World,    Oct.   15,   1921,    p.   763. 

Stickney)  and   Mahar.,    General   Electric  Revew,   Dec.,    1921.    p.    1023. 

203 


TABLE  2— Suggested  Schedules  for  Cleaning  Reflectors 

Where  direct  lighting  systems  are  used,  i.  e.,  where  there  are  no  reflecting  or  diffusing 
surfaces  concave  upward  to  invite  dirt  accumulation,  the  interval  of  cleaning  should 
be  about  as  follows: 


Characteristic  of  Location 

Interval  in  Days 
if  Units  are 
Wiped  out* 

Interval  in  Days 
if  Units  are 
Thoroughly  Washed 

Very  Dirty                                     

3 

5 

Dirtv   ' 

7 

10 

L     3 
Average  ...                       

15 

20 

Clean.. 

30 

40 

Where  open  semi-indirect  or  totally  indirect  units  are  used: 


Characteristic  of  Location 

Interval  in  Days 
if  Units  are 
Wiped  out* 

Interval  in  Days 
if  Units  art 
Thoroughly  Washed 

Dirty...                                                  ..... 

5 

7 

Average                  

10 

15 

Qean         

20 

30 

*  Washing  every  third  or  fourth  interval  assumed. 


tioned  here  to  show  that  the  light  wasted  through  inadequate 
maintenance  is  not  simply  light  over  and  above  that  which  is 
needed  for  efficient  operation  of  the  plant;  it  is  light  which  has 
an  important  effect  on  production  and  as  such  has  a  potential 
value  far  in  excess  of  its  purchase  price. 

Another  effect  of  inadequate  maintenance  which  is  almost 
always  entirely  overlooked  is  that  of  increasing  glare  and  of 
making  shadows  sharper  and  heavier.  A  bright  bulb  against  a 
dirty  reflector,  or  a  bright  unit  against  a  blackened  ceiling  ac- 
centuates glare.  The  density  of  shadows  depends,  among  other 
ihings,  upon  the  area  of  the  light  sources,  and  where  reflectors 
are  dirty,  their  contribution  of  diffused  light  is  lost. 

Systematic  Maintenance 

Because  the  rate  of  depreciation  depends  so  greatly  upon  in- 
dividual conditions,  it  is  difficult  to  formulate  schedules  which 
do  more  than  roughly  indicate  suitable  cleaning  periods.  The 
schedules  of  Table  2  are,  however,  representative  of  good  prac- 
tice. By  far  the  best  check  on  the  illumination  is  obtained  by 
frequent  foot-candle  reading  at  various  stations  throughout  the 
f,lant.  These  readings  are  easily  and  quickly  made  by  means 
of  the  foot-candle  meter,  illustrated  in  Fig.  3.  A  simple  record 
of  readings  such  as  that  shown  in  Fig.  4  will  reveal  at  a  glance 


204 


ihe   condition  of  the  lighting  system   and  will   indicate  where 
trouble  is  brewing  before  it  becomes  serious. 

There  is  a  considerable  difference  .between  merely  wiping 
out  a  unit  and  washing  it  thoroughly.  The  difference  is  more 
•narked  in  some  units  than  in  others.  With  the  exception  of  mjir- 
rored  reflectors,  and  of  plaster  or  composition  units  (which  are 
^eadily  cleaned  with  sandpaper  or  a  stiff  wire  brush)  all  require 
a  thorough  washing  at  least  as  often  as  every  third  or  fourth 
cleaning  period.  Warm  water  and  soap  or  any  of  the  prepared 
<  leaners  used  in  the  bathroom  of  a  home  are  effective  in  nearly 
all  cases.  Mirrored  units  require  special  attention  to  avoid  in- 
jury to  the  backing. 

Inspection  of  lamp  bulbs  for  possible  blackening  should  be 
made  at  the  regular  cleaning  period,  and  if  a  bulb  appears  con- 
siderably darkened  it  should  be  replaced.  The  cleaning  should 
:jot  be  considered  complete  until  the  unit  has  been  lighted  to  in- 
sure that  it  operates.  The  cleaner  should  carry  a  supply  of 
lamps  of  the  proper  size  and  voltage  with  him  so  that  failures 
may  be  replaced  immediately. 

Where  proper  cleaning  is  rendered  hazardous  because  of  the 
Jifficulty  of  getting  at  the  units,  disconnecting  hangers,  of  which 
there  are  several  types  available,  may  be  used  to  advantage. 
Where  these  are  employed,  the  work  can  sometimes  be  entrusted 
to  employees  who  could  not  otherwise  safely  handle  it. 

The  walls  and  ceiling  will  have  lost  much  of  their  reflecting 
effectiveness  before  they  appear  badly  in  need  of  refinishing  and 
the  consideration  of  lighting  economy  often  dictates  the  refinish- 
ing of  an  interior  before  the  expenditure  from  an  appearance 
standpoint  suggests  itself.  The  foot-candle  meter,  which  meas- 
ures the  combined  effect  of  all  possible  causes  of  depreciation, 
will  enable  the  maintenance  men  to  watch  the  gradual  deprecia- 
tion as  shown  on  their  records  and  to  determine  when  refinish- 
ing is  necessary.  A  white  paint  or  plaster  surface  absorbs  less 
light  than  any  other  interior  finish,  and  the  former  is  particularly 
adapted  to  factory  interiors.  The  color  of  the  side  walls  for  the 
^  or  6  feet  next  the  floor  has  no  material  effect  upon  either  the 
color  or  quantity  of  the  illumination,  and  a  dark  color  is  pre- 
ferred because  it  is  restful  to  the  eyes  and  because  it  does  not 
show  dirt  and  smudge  readily. 

The  cost  of  maintaining  a  system  properly  is  largely  one  of 
labor  and  will,  of  course,  vary  considerably.  In  large  industrial 

205 


plants  a  small  maintenance  department  is  necessary  for  accom- 
plishing effective  results.  In  small  buildings  one  employee  may 
be  able  to  handle  the  work  satisfactorily.  Where  the  responsi- 
bility is  definitely  assigned  to  a  reliable  employee  and  he  is 
given  sufficient  authority  to  see  that  the  work  is  properly  done, 
the  entire  routine  may  .be  placed  upon  a  systematic  basis.  In  a 
building  or  plant  of  sufficient  size  to  require  the  entire  time  of 
it  least  one  man,  the  cost  of  proper  cleaning  should  not  exceed  3 
cents  per  unit  per  cleaning  in  the  case  of  open  reflectors.  With 
open  semi-indirect  or  totally  indirect  fixtures,  the  cost  will  be 
considerably  higher.  The  enclosed  semi-indirect  units  which  have 
recently  appeared  on  the  market  are  slow  to  collect  dirt  and 
compare  favorably  with  direct  lighting  open  reflectors  in  clean- 
ing. In  some  cases,  it  will  be  desirable  to  have  the  cleaning 
done  by  window  cleaning  companies,  some  of  which  have  es- 
tablished definite  departments  to  handle  this  work  as  a  part  of 
their  regular  service. 


TO  RESTORE  A  LIGHTING  SYSTEM 

1.  Wash    reflectors    and    lamps    thoroughly    at    least 
every   third   or   fourth    cleaning   period.      See    Cleaning 
Schedule,  Table  2. 

2.  Fill    empty    sockets    and    replace   burned-out    and 
blackened  lamps  with  new  ones  of  the  correct  size  and 
proper  voltage  rating.     The  voltage  rating  of  the  lamp 
should  be  at  least  no  higher  than  the  voltage  at  the  socket 
when  the  system  is  in  use.    Avail  yourself  of  the  service 
of  the  lamp  manufacturer  in  determining  what  the  volt- 
age rating  of  your  lamp  should  be. 

3.  Refinish  ceiling  and  upper  part  of   side  walls  in 
white  or  in  a  very  light  cream  color. 

4.  Make  some  reliable  employee  responsible  for  the 
maintenance  of  the  lighting  system  and  give  him  suffi- 
cient authority  to  enable  him  to  get  the  work  done. 


206 


PART  XV 
MODERN  PRACTICE  IN  STREET  LIGHTING 

In  considering  a  plan  of  street  lighting  for  a  city  it  is  neces- 
sary to  observe  carefully  the  different  requirements  of  each  class 
of  street  to  the  end  that  the  most  efficient  result  possible  may  be 
obtained  from  the  expenditure.  It  is  obvious  that  the  thorough- 
fares of  the  principal  business  district  will  require  the  greatest 
amount  of  illumination,  for  in  this  section  there  is  congestion  of 
foot,  vehicle,  and  street  car  traffic.  The  principal  thoroughfares 
leading  outward  from  the  center  of  the  city  and  the  streets  in 
the  .wholesale  and  manufacturing  districts  likewise  carry  much 
traffic  of  a  high  speed  nature  and  must  be  lighted  accordingly. 
In  the  residential  streets,  which  do  not  carry  through  traffic  to 
any  extent,  requirements  for  illumination  from  the  standpoint  of 
traffic  are,  of  course,  much  less  severe.  In  certain  outlying  dis- 
tricts appropriation  allowances  sometimes  make  it  necessary  to 
reduce  the  lighting  to  a  system  of  small  marker  lights  for  cor- 
ners only. 

It  should  be  recognized,  of  course,  that  the  highest  intensity 
of  illumination  in  the  principal  business  streets  of  large  cities 
at  the  present  time  is  not  greater  than  would  be  desirable  for 
all  streets  of  the  city,  except  for  the  cost.  However,  because  of 
the  very  great  areas  to  be  covered,  and  the  limited  appropria- 
tion available,  it  may  be  possible  to  provide,  perhaps,  only  i/io 
as  much  light  on  residential  side  streets  as  in  the  principal  busi- 
ness section.  In  consequence  of  these  very  low  levels  of  illu- 
mination which  must  suffice  for  all  except  the  limited  White 
Way  district,  it  becomes  especially  necessary  to  exercise  the 
greatest  care  to  see  that  the  available  illumination  is  so  placed 
£.nd  directed  that  it  contributes  most  effectively  towiard  safety 
from  crime  and  accident,  toward  the  comfort  and  convenience 
of  those  using  the  streets,  and  toward  improving  the  day  and 
night  appearance  of  the  street. 

Not  only  are  there  differences  in  local  conditions  to  be  con- 
sidered in  planning  street  lighting,  but  also  the  developments  in 
the  power  of  lamps  and  in  the  efficiency  of  equipment  have  been 
so  rapid  that  there  are  not  as  yet  fully  definite  standards  of  de- 
sign which  are  generally  adhered  to  for  the  different  classes  of 
streets.  However,  there  are  certain  tendencies  which  have  come 
about  as  a  result  of  experience  with  different  types  of  installa- 
tions under  various  conditions.  Table  I  contains  a  summary  of 

207 


practice  as  to  lamp  size,  mounting  height,  and  spacing  applica- 
ble to  the  different  classes  of  streets. 


Principal  Business  Streets 

For  important  business  streets  in  cities,  the  most  widely  fa- 
vored method  of  lighting  consists  in  the  use  of  single  light  or- 

Table  No.  i — Summary  of  Modern  Street  Lighting  Practice 

Street  Class  Size  of  Lamps*  Mounting        Spacing 

Height 

Business    District 600,  looo,  1500,  and  2500  C. P.       14-18  ft.         80-125  ft. 

Boulevards  and  Parks. 250,  400,  600,  and  1000  C.P.       14-20 ft.         80-200 ft. 

Wholesale  and  Manu- 
facturing Districts 
and  Thoroughfares .  .400,  600,  1000,  and  1500  C.P.         20-25  ft.       150-300  ft. 

Residential    250,  400,  and  600  C.P.  14-20  ft.       150-300  ft. 

Outlying  Districts 
and   Alleys    100  and  250  C.P.  14-20  ft.       150-300  ft. 

Highways    250  and  400  C.P.  25-35  ft.       300-600  ft. 

The  lower  mounting  heights  should  be  adopted  only  with  the  smaller 

lamps  and  at  the  closer  range  of  spacings.     For  the  larger  lamps  and  the 

wider  spacings  the  upper  range  of  mounting  heights  is  preferable. 


*  The  rated  lumen  output  of  street-series  Mazda  lamps  is  equal  to  ten 
times  the  candle-power  rating. 

namental  standards  mounted  at  heights  from  14  to  18  feet  and 
spaced  opposite  each  other  at  distances  of  80  to  120  feet.  For 
v'ery  narrow  streets  the  lamps  may  be  placed  on  one  side  only  or 
staggered  at  the  same  spacing.  An  important  increase  in  effi- 
ciency is  secured  by  the  use  of  lamps  of  600,  1,000,  1,503,  or 
2,500  candlepower  instead  of  the  3,  4,  or  5  light  clusters  using 
tmall  lamps  which  were  the  vogue  before  the  introduction  of 
the  high-powered  gas-filled  incandescent  lamp.  Typical  equip- 
ments of  modern  character  are  shown  in  Fig.  i.  There  is  at 
present  a  very  noticeable  tendency  to  depart  from  the  use  of 
the  opal  ball  or  globe,  and  to  use  instead  a  lantern  structure, 
which  by  many,  is  considered  more  pleasing  in  appearance. 
Cleveland  was  the  first  large  city  to  adopt  equipment  of  this 
character  and  has  something  over  1,500  lantern  standards,  using 
1,000  and  1,500  candlepower  incandescent  lamps. 

Instead  of  the  single  lamp  standards  spaced  relatively  close 
together,  some  cities  have  adopted  standards  carrying  two  or 
even  three  high-powered  lamps  mounted  20  to  30  feet  above 
the  street  and  spaced  150  to  200  feet  apart.  The  resultant  ef- 
lective  illumination  is  not  greatly  different  from  the  more  usual 

208 


arrangement  and  the  exceptionally  high  mountings  minimize 
any  possibility  of  glare  from  the  lamps.  On  the  other  hand, 
there  appears  to  be  much  weight  on  the  side  of  those  who  con- 
tend that  on  business  streets  the  surrounding  brightness  of 
buildings,  show  windows,  etc.,  is  such  that  there  is  no  possibil- 


Fig.  i. — Typical  Ornamental  Lamp  Equipments.     These  Designs  Accom- 
modate 600  to  2500  Candlepower  Lamps  for  Business  Streets. 
Equipment    of    the    Same    General    Character,    but    De- 
signed for  Smaller  Lamps,  is  used  for  Ornamental 
Boulevard  or  Residence  Street  Lighting 

ity  of  serious  glare  even  with  the  large  lamp  at  the  lower  mount- 
ing of  15  to  18  feet  and  that  the  desirable  "White  Way"  effect 
is  enhanced  by  lanterns  at  these  heights  spaced  80  to  90  feet 
apart. 

The  demand  for  higher  levels  of  illumination  on  business 
streets  has  led  in  some  cities  to  the  consideration  of  lamp  stand- 
ards carrying  two  or  three  1,000  or  1,500  candlepower  lamps 

209 


each  and  spaced  no  more  widely  than  previous  single  lamp  in- 
stallations. It  is  quite  possible  that  there  will  be  an  increased 
development  of  this  tendency,  especially  in  the  larger  cities 
where  the  crowds  from  evening  business  and  amusements  have 
become  such  that  in  many  cities  "White  Way"  systems,  which 
were  installed  quite  largely  as  an  ornamental  or  advertising  fea- 
ture, are  even  now  barely  adequate  from  the  standpoint  of  light- 
ing for  safety. 


Fig.  2 — Types  of  Pendant  Refractor  Fixtures  for  Mast  Arm  Suspension 

Thoroughfares 

The  thoroughfares  leading  out  from  the  business  section 
and  the  streets  in  the  wholesale  and  manufacturing  districts  have 
developed  severe  requirements  for  lighting  under  the  new  con- 
ditions of  transportation.  These  streets  carry  high  speed  traf- 
fic and  are  the  location  of  a  large  percentage  of  street  accidents, 
particularly  at  night  in  those  cases  where  a  proper  provision  for 
Hghting  has  not  yet  been  made.  In  some  instances  it  is  found 
practical  to  extend  the  high  intensity  lighting  of  the  business 
district  to  include  these  streets.  However,  this  usually  involves 

210 


a  greater  expenditure  than  is  permissible,  and  in  any  event  the 
light  colored  building  surroundings  characteristic  of  the  busi- 
ness section  are  lacking  in  most  of  these  thoroughfares  and  for 
this  reason  as  well  as  because  of  the  wider  spacing,  it  is  desira- 
ble to  use  a  greater  mounting  height  for  the  lamps  in  order  to 
avoid  the  blinding  effect  of  glare.  A  fair  provision  for  thor- 
oughfares outside  the  business  district  is  an  arrangement  of 
iamps  of  600,  i  ,000,  or  1,500  candlepower  spaced  from  150  to 


Fig.  3. — Ornamental  Bracket  Standards  for  Lighting  Thoroughfares  and 

Boulevards.     In  These  the   Height  to  the  Lamp  is  Approximately 

20  ft.     Similar  Designs  for  Smaller   Lamps  are  Made  with 

Heights  of  About  16  ft.  for  Residence  Streets 

250  feet  apart,  or,  at  a  maximum,  300  feet.  If  the  street  is  very 
wide  it  may  be  necessary  to  consider  each  side  as  a  separate 
street  and  provide  lighting  accordingly.  The  mounting  height 
should  be  20  or  preferably  25  feet  in  order  to  remove  the  bright 
light  sources  farther  from  the  line  of  vision,  and  also  in  order 
to  obtain  a  better  spread  of  illumination.  In  the  past,  especially 
where  there  were  wooden  pole  lines  on  the  streets,  it  has  been 
common  practice  to  use  a  lighting  fixture  such  as  illustrated  in 

211 


Fig.  2,  suspended  from  a  mast  arm.  The  mast  arm  has  the  vir- 
tue of  bringing  the  lamp  out  over  the  street  surface,  thereby 
causing  the  light  rays  to  clear  low  hanging  foliage  of  adjacent 
trees.  Bringing  the  lamp  over  the  pavement  also  increases  the 
possibilities  of  seeing  objects  by  silhouette  against  the  bright 
£pot  of  light  beneath  the  lamp  or  against  the  bright  streak  or 
glint  reflections  from  the  pavement.  This  is  an  especial  advant- 
age in  the  case  of  much  traveled  streets  which  soon  become 
blackened  from  oil,  but  are  polished  by  wear  and  have  a  glossy 
surface  when  wet.  Under  these  conditions,  a  very  large  depend- 
ence m'ust  be  placed  upon  seeing  objects  in  silhouette  against 
the  glint  from  the  pavement  on  account  of  the  low  level  of 
general  illumination. 

The  fixture  in  Fig.  2  is  equipped  with  a  prismatic  refractor 
and  this  feature  is  usually  incorporated  in  the  equipment  for  this 
i.ype  of  lighting,  since,  by  means  of  the  refractor,  the  candle- 
power  of  the  lamp  at  angles  directed  to  the  zone  midway  be- 
tween the  lamps  may  be  increased  practically  100  per  cent. 
Therefore,  the  light  delivered  on  the  street  is  much  greater  than 
with  equipment  which  does  not  take  full  advantage  of  the  up- 
ward rays  from  the  lamp  filament. 

Recent  designs  of  lighting  equipment  for  thoroughfares  and 
boulevards  have  shown  the  results  of  efforts  to  retain  the  effi- 
ciency of  light  distribution  of  the  rriast  arm  pendant  refractor 
unit  type  of  lighting,  and,  at  the  same  time,  to  obtain  a  construc- 
tion which  would  add  to  the  appearance  of  the  street.  Some  of 
these  bracket  type  lighting  standards  for  thoroughfares  or  boule- 
vards are  illustrated  in  Fig.  3. 

Residence  Streets 

Where  residence  streets  carry  a  large  amount  of  through 
traffic  they  are  in  effect  thoroughfares  and  should  be  lighted  as 
such.  However,  in  every  city  there  is  a  large  percentage  of 
street  mileage  not  used  for  through  travel  and,  therefore  not 
subject  to  a  large  amount  of  high  speed  traffic.  Even  in  these 
streets,  however,  sufficient  illumination  must  be  provided  to  en- 
able discernment  of  objects  and  obstructions  in  the  pavement 
by  one  traveling  at  a  moderate  rate  of  speed.  Illumination  for 
sidewalks  must  also  be  provided  which  is  adequate  for  com- 
fortable walking  and  which  does  not  leave  such  dark  shadows 
behind  tree  trunks  as  might  serve  as  possible  hiding-  places 
for  footpads.  Residence  streets  are  very  commjonly  well  pro- 

212 


Ornamental  Two-Light  Post  to  Harmonize  with  the  Building 


Euclid  Avenue,  Cleveland,  Illuminated  by  1500  Candlepower  Incandescent 
Lamps  in  Ornamental  Lanterns  Spaced  85  feet  apart. 

213 


Prospect    Avenue,    Milwaukee,    Wis.      15    foot    concrete 

posts,  120  feet  apart,  42  lumens  per  lineal  foot  of  street. 

Average  intensity,  0.2  foot  candles 


Albany-Schenectady    Highway    Illuminated    by    250    Candlepower 

Mazda   Lamps   in    Parabolic   Units    Spaced   300   to    500    Feet 

Apart   and   Mounted  30   Feet   Above   the   Ground 

214 


vided  with  trees;  hence,  unless  the  lamp  is  suspended  over  the 
center  of  the  street,  it  is  often  necessary,  in  order  to  avoid  a 
large  loss  of  I'-ght,  to  use  somewhat  lower  mounting  heights 
than  would  be  desirable  on  streets  without  trees.  However,  in 
view  of  the  lower  candlepowfer  of  the  lamps  commonly  used  (250 
candlepower),  they  may  .be  placed  as  low  as  15  feet  above  the 
street  without  undue  glare,  provided  the  light  is  properly  dif- 
fused and  directed.  When  larger  lamps  are  used  and  at  wider 
spacings,  heights  of  18  or  20  feet  are  considered  preferable  prac- 


WH1TE  GLASS  GLOBE, 

Fig.  4. — Illumination  from  250  Candlcpow.cr  Lamps  Computed  for 

Residence  Streets 

Top:   Refractor   Lantern   Bracket   16  ft.   Above   Street 
Bottom:    Opal   Globe  on    10   ft.    Post 

tice.  In  this  matter  of  adequate  height  the  ordinary  wood  pole 
bracket  installations  have  been  better  than  many  systems  of  or- 
namental standards  supplied  from  underground  wiring.  Some 
of  these  systems  have  used  globes  mounted  on  upright  posts 
only  10  or  u  feet  in  height  and  while  tree  foilage  is  success- 
fully avoided,  the  units  are  likely  to  prove  very  glaring  in  the 
eyes  of  drivers,  pedestrians,  or  of  people  on  porches.  Further- 
more, a  very  close  spacing  must  be  adopted  if  all  sections  of 
the  street  are  to  be  illuminated.  Particularly  on  a  curved  road, 
glare  from  lamps  placed  too  low  may  so  interfere  with  vision 
that  the  lamps  may  actually  become  a  source  of  danger  to  auto- 
mobile drivers.  In  view  of  this,  in  recently  designed  systems, 
there  has  been  a  tendency  to  adopt  a  minimum  height  of  15  feet 
for  ornamental  posts  on  residence  streets.  Also  ornamiental 
bracket  designs  have  been  developed,  bringing  the  lamp  16  feet 
or  more  above  the  street  and  with  a  bracket  length  of  4  or  5  feet 


to  assist  in  clearing  the  foliage.  When  these  equipments  carry 
well  designed  refractor  fixtures,  the  light  utilization  is  as  great 
as  from  the  efficient  but  often  unsightly  wood  pole  brackets. 
Fig.  4  illustrates  the  remarkable  increase  in  effectiveness  from 
equipment  of  this  character  compared  with  a  system  of  low 
mounted  upright  ball  globes. 

Lamp  spacings  on  residence  streets  vary  greatly.  Where 
overhead  wood  pole  distribution  is  used  and  the  appropriation 
allowance  is  very  limited,  spacings  of  the  order  of  300  feet  may 
be  used  to  give  fair  lighting,  provided  there  are  no  trees  to  ob- 
struct the  spread  of  light.  On  the  other  hand,  spacings  of  100 
feet  or  even  less  are  not  uncommon  for  underground  distribu- 
tion supplying  low-mounted  ornamental  units.  Unless  the  in- 
terference from  trees  is  excessive,  spacings  of  150  to  200  feet  are 
found  satisfactory.  The  lamps  are  customarily  staggered  to  re- 
duce tree  trunk  shadows. 
Outlying  Districts  and  Alleys 


Fig.    5. — Radial   Wave    Reflector   and    Bracket    for    Small    Lamps 

Fig.  5  illustrates  a  typical  bracket,  with  a  radical  wave  re- 
flector suitable  for  attachment  to  wooden  poles  or  buildings 
fn  outlying  districts  or  alleys.  This  equipment  using  the  100 
candlepower  lamp  and  mounted  15  or  20  feet  above  the  streets 
forms  a  very  inexpensive  type  of  equipment  for  those  locations 
where  small  lamps  are  all  that  can  be  provided  and  where,  con- 
sequently, a  wide  spread  of  light  and  the  matter  of  protection 
against  glare  is  of  less  importance. 
Highways 

Where  it  is  desired  to  illuminate  only  the  roadway  without 
particular  regard  for  the  surroundings,  special  types  of  equip- 
ment are  available. 

216 


In  one  design,  the  unit  is  made  up  of  nested  parabolic  con- 
struction so  as  to  direct  a  high  intensity  up  and  down  the  road 
with  very  little  side  lighting.  If  mounted  high,  say  25  to  35  feet, 
and  spaced  from  300  to  600  feet  apart  with  250  or  400  candle- 
power  lamps,  equipment  of  this  kind  provides  an  illumination 
which  is  of  very  great  assistance  to  night  drivers  in  avoiding 
accidents. 
The  Necessity  of  Maintenance  in  Street  Lighting 

If  the  full  effectiveness  of  a  street  lighting  system  is  to  be 
secured,  it  is  fundamental  that  a  regular  and  adequate  mainten- 
ance schedule  be  adopted.  As  the  following  investigation  strik- 
ingly brings  out,  it  is  quite  possible  for  an  installation  to  depre- 
cjate  to  such  an  extent  as  to  deliver  only  one-third  the  amount 
of  light  on  the  street  which  it  would  be  expected  to  deliver  under 
good  operating  practice. 

When  the  system  on  which  the  following  data  were  obtained 
was  first  placed  in  service,  it  was  considered  to  be  one  of  the 
best  designed  installations  in  the  country.  However,  after  it 
had  been  in  operation  for  approximately  one  year,  to  even  the 
cr.sual  observer  the  amount  of  light  emitted  by  the  fixtures 
was  far  below  that  emitted  when  the  system  was  first  turned  on. 
The  appearance  of  the  units  when  lighted  indicated  that  the 
glassware  was  dirty,  and  also  that  the  lamps  were  burning  con- 
siderably under  rated  efficiency.  In  order  to  determine  just  what 
percentage  of  the  decrease  in  candlepower  should  be  attributed 

Table  No.  2 

Per  Cent  Per  Cent  Equivalent 

Normal  Increase 

Candlepower  in  Light  Size  of  Lamp 

As   found    31                            ...  185  C.  P. 

Unit   thoroughly    cleaned....       67                           116  400  C.  P. 

New  lamp  of  proper  rating..       87                             30  520  C.P. 

Rated  current  in  new  lamp..      100                             15  600  C.P. 

10  the  various  factors  involved,  photometric  and  electrical  meas- 
urements were  made  on  two  of  the  units.  Candlepower  meas- 
urements of  the  equipment  as  found,  and  when  thoroughly 
cleaned  with  soap  and  water,  were  taken.  The  current  through 
the  lamps  was  checked,  and  the  old  lamps  found  in  the  fixtures 
were  brought  mto  the  laboratory  for  lum'en  rating.  The  elec- 
trical measurements  showed  that  the  lamps  were  burning  below 
rated  amperage.  An  inspection  of  the  lamps  indicated  that  some 
had  burned  much  longer  than  their  rated  life,  and  the  consequent 
blackened  bulbs  and  sagged  filaments  gave  evidence  that  they 
were  operating  at  a  very  low  efficiency. 

The  accompanying  chart  (Fig.  6)  and  the  tabulation  in  Table 

217 


No.  2  plotted  for  one  of  the  units,  indicates  the  weight  of  the 
various  factors  accountable  for  the  decrease  in  efficiency  of  the 
system.  Although  6oo-candlepower  lamps  are  used  in  this  in- 
stallation the  photometric  measurements  show  that  the  light  out- 
put of  the  fixture  as  found  was  only  equivalent  to  the  output 
which  would  be  obtained  with  a  i85~candlepower  lamp  operated 
at  rated  current  in  a  clean  fixture.  By  washing  the  lamp  and 
glassware  the  equivalent  lamp  size  was  increased  to  4OO-candle- 
power,  an  increase  of  116  per  cent.  The  substitution  of  a  new 
jamp  of  proper  rating  raised  the  equivalent  lamp  size  to  520- 


Fig.  6. — Equivalent  Candlepower  of  Lamp,  which,  if  Operated  at  Rated 

Current  in  a  Clean  Fixture,  would  Duplicate  Performance 

of  Unit  Tested 

tandlepower,  an  increase  of  30  per  cent.  With  the  correct  cur- 
rent through  the  lamp  the  light  output  was  increased  still  an- 
other 15  per  cent  and  was  brought  up  to  the  rated  value,  6oo-can- 
dlepower. 

The  above  data  forcefully  bring  out  the  necessity  of  a  rigidly- 
adhered-to  maintenance  schedule,  such  as  the  following,  if  it  is 
desired  to  secure  an  installation  which  will  be  satisfactory  from 
the  standpoints  both  of  appearance  and  illumination  effective- 
ness. 

1.  A  systematic  and  regular  cleaning  schedule  should  be  in 
operation. 

2.  Lamps  which  have  lived  far  beyond  their  rated  lives  and 
whose  filaments  have  sagged  or  whose  bulbs  have  become  black- 
ened should  be  removed  from  the  system. 

3.  The  current  through  the  lamps  should  be  maintained  at 
the  rated  amperage. 

218 


PART   XVI 
ELECTRICAL  ADVERTISING 

Statistics  obtained  in  Cleveland,  Ohio,  in  which  the  sign 
development  may  be  considered  fairly  typical  of  large  cities  in 
general,  show  that  in  the  past  two  and  one-half  years,  in  spite 
of  a  falling  off  in  the  total  energy  supplied  by  the  central  sta- 
tion, the  electrical  advertising  load  has  more  than  doubled.  That 


Conrxected 


E.L&CTRICAL  ADVERTISING  LOAD 

Fig.   1 — The  growing  appreciation  of   electrical  advertising  is  attested  by  the 
increase  in  the  energy  required.      (Data   obtained   in   Cleveland.) 

this  has  occurred  without  an  organized  selling  effort  and  at  a 
time  when  the  total  expenditure  for  all  forms  of  advertising  was 
being  sharply  cut,  is  significant  of  the  growing  appreciation  of 
the  value  of  electrical  advertising.  The  return  of  business  to  a 
competitive  basis — the  necessity  for  aggressive  sales  effort — • 
is  an  influence  which,  aided  by  the  increasing  skill  and  clever- 
ness of  the  sign  designer,  insures  a  rapid  development  in  sign 
application. 


LAUNDRY  12 
DANCE  HALUS  12 
R.&AL  E-VTATE-12 
I    MAR.K&TS  20 

I    DePAR-TME-NT  STORES  22 


TH&AT&R.328 

Cuues29 

Music  34- 
TOBACCO  55 

FUR.NITUR.e37 
&L&CTRJCAL.  S 

BOWLING  59 


J>&NTlSTt>  c-TC  75 

SHO&S  91 
BANKS  95 


MOTION  PICTURES  I3O 
CLOTHING   136 

AUTOMOBIL&  169 
ORAJGS  184 


ReSTAUftAMTS 


Fig.  2 — Distribution  of   Signs  According  to   Classes  of   Users. 
(Cleveland  Electric  Signs.) 


3IQ 


FORMS  OF  ELECTRICAL  ADVERTISING 

There  are  four  principal  forms  of  electrical  advertising. 
These  are : 

1.  Electric  signs  of  the  exposed  or  enclosed  lamp  type; 

2.  Illuminated  Bulletin  and  Poster  Boards; 

3.  Building  Outline  and  Marquee  lighting; 

4.  Floodlighted  advertisements. 

A  display  of  whatever  form  must  have  :  first,  attracting  power, 
or  the  ability  to  gain  attention;  second,  selling  power,  or  the 
ability  to  impress  a  message  and  make  it  endure.  In  the  majority 
of  displays,  a  third  essential  is  legibility,  or  the  property  of 
showing  word  or  picture  in  well  defined,  clean-cut  lines. 

Brightness  and  motion  are,  of  course,  two  of  the  major  char- 
acteristics of  electrical  advertising  by  which  the  designer  obtains 
attracting  and  selling  power.  In  no  other  form  of  advertising 
does  he  have  the  opportunity  to  capitalize  these  features  to  so 
great  an  extent.  Originality,  beauty,  and  color  are  tools  which 
the  designer  uses  according  to  his  ability  and  the  extent  of  the 
funds  available.  The  picture,  border,  size,  and  position  of  the 
sign  are  factors  which,  obviously,  bear  tremendously  on  the  ef- 
fectiveness of  the  display. 

Exposed  Lamp  Signs 

Of  all  the  requirements  of  an  exposed  lamp  sign,  none  is 
more  important  than  legibility.  Whether  the  message  is  car- 
ried by  word  or  by  picture,  clear-cut,  sharply  defined  lines  of 
light  are  essential. 

The  distance  at  which  a  sign  will  appear  legible  depends  upon 
the  dimensions  of  the  letters  or  pattern,  the  candlepower  of  the 
lamps,  the  color  of  the  light,  and  the  brightness  of  the  back- 
ground. 

Maximum  legibility  distance  is  directly  proportional  to  size, 
and,  for  a  given  pattern,  is  determined  by  the  separation  of  the 
distinguishing  strokes.  When  these  strokes  appear  to  approach 
each  other  so  closely  that  they  blend,  the  pattern  becomes  il- 
legible. This  blending  occurs  when  details  lie  closer  together 
than  approximately  one  minute  of  arc. 

The  effect  of  illuminating  a  letter  or  pattern  is  to  decrease 
the  maximum  distance  at  which  it  is  legible.  The  reason  for 
this  is  that  a  bright  object  always  appears  larger  than  a  dark 
one.  An  exposed  incandescent  filament  viewed  at  close  range 
against  a  dark  background  will  appear  perhaps  one-third  as 
large  as  the  glass  bulb ;  as  the  observer  moves  away  the  spot 


220 


0        1000     2000     3000    4000     5000     6000    7000      8000     9000     10,000 
Distance-  Feet 

Fig.  3 — Maximum  Legibility  Distance  of  Signs  of  Average  Number 

of  Letters 

Based  on  average  street  illumination  and  clear  air  when  seen  by 
normal  eyes  and  when  the  determining  letter  is  a  Gothic  E  or 
its  equivalent.     The  dotted  line  shows  a  theoretical  maxi- 
mum distance  ordinarily  unattainable  even  under  the 
best  conditions  encountered  in  service 

of  light  apparently  increases  in  size,  expanding  until  it  fills 
the  bulb,  and  continuing  to  grow  larger  and  larger.  The  effect 
of  this  irradiation,  as  it  is  called,  is  to  increase  the  width  of  the 
strokes  in  a  pattern,  decrease  the  separation  between  strokes, 
and  hence  reduce  the  legibility  distance  of  the  sign.  The  ap- 
parent size  of  a  spot  of  light  from  an  exposed  filament  depends 
upon  the  distance  of  the  lamp  from  the  eye,  the  tip  candlepower 
of  the  lamp,  and  the  brightness  of  the  background  against  which 
the  lamp  is  seen. 

The  effect  of  increasing  the  tip  candlepower  of  the  lamps  in 
a  sign  is,  first,  to  increase  the  attracting  power,  and  second,  to 
decrease  the  maximum  legibility  distance.  Unquestionably,  the 
bright  sign  is  more  effective  than  the  dim  one.  The  proper  pro- 
cedure in  design  is  therefore  to  use  lamps  of  a  size  which  will 
compel  attention  and  to  make  the  letters  large  enough  with 
these  chosen  lamps  to  obtain  the  desired  legibility  distance. 

Increase  of  background  brightness  and  surroundings  such 
as  the  light  from  a  border  of  lamps  about  a  sign,  other  displays, 

221 


or  the  street  illumination,  has  the  effect  of  reducing  the  apparent 
spot  size  and  so  of  increasing  legibility  distance.  This  means,  of 
course,  that  a  sign  in  a  brightly  lighted  district,  where  competi- 
tion is  keener,  may  be  made  brighter  and  more  attractive  than 
a  sign  of  the  same  size  in  a  darker  district  and  yet  be  legible 
over  as  great  a  distance. 

The  color  of  the  light  in  a  sign  affects  the  legibility  distance 
but  it  is  used  chiefly  to  obtain  greater  attracting  power  and  more 
artistic  and  spectacular  effect.  As  usually  applied,  its  effect  upon 
legibility  distance  is  of  secondary  importance. 

From  information  obtained  in  extensive  tests,  it  is  possible 
to  evaluate  the  effect  of  the  factors  discussed  above  and  present 

Table  i 
Lamp  Spacing  to  Provide  Unbroken  Lines  of  Light 


Clear 
Glass 
Lamp 
Spacing 
Inches 

3     . 
4     . 
5     . 
6     . 
7     . 
8     . 
9     . 
10     . 
11      . 
12     . 
13     . 
14     . 
15     . 
16     . 

/  

10 
Watt 
Lamps 

D 
Wh 

-Comparatively 
25            50 
Watt     Watt 
Lamps  Lamps 

stance 
en   the 
Bright- 
75 

Watt 
Lamps 

to      Observer 
Surrounding   11 

in       Feet 
umination   is: 
—Comparative] 
25            50 
Watt     Watt 
Lamps  Lamps 

y     Dark 
75 
Watt 
Lamps 
* 
* 
* 
* 
* 

440 
500 
570 
630 
690 
750 
810 
870 
940 
1000 

V 

La 

5( 

5. 
6 
6< 
7, 
7; 
& 
8< 

100 
/att 
mps 

¥ 

)0 

50 
10 
50 
20 
?0 
50 
)0 

100 
Watt 
Lamps 

10 
Watt 
Lamps 

480 
630 
790 
950 

420 
560 
700 
840 
990 

* 
500 
620 
740 
870 
990 

* 

* 

570 
680 
800 
910 

* 
* 

* 

610 

720 
820 
920 

290 

390 
490 
590 
690 
790 
880 
980 

* 

330 
410 
500 
580 
660 
740 
830 
910 
990 

* 
* 
* 

420 
490 
560 
630 
700 
770 
840 
900 
970 

*  For  distances  less  than  the  lowest  given  in  the  table,  it  is  impossible  to 
obtain  the  appearance  of  a  continuous  line  of  light.  If  the  exposed  lamp 
design  is  used  for  signs  in  such  locations,  the  spacing  should  be  made  as 
small  as  mechanically  possible. 


data  which  is  applicable  to  practical  sign  design.  From  the 
curve  of  Fig.  3,  the  maximum  legibility  distance  of  signs  having 
an  average  number  of  letters  (5  to  10),  when  made  up  in  different 
heights  may  be  readily  approximated.  In  Table  1  are  given  the 
spacing  distances  required  between  lamps  of  various  sizes  to 
present  an  unbroken  line  of  light  when  located  in  bright  sur- 
roundings and  when  located  in  dark  surroundings.  A  chart, 
Table  2,  suggests  which  sizes  and  kinds  of  lamps  are  best  suited 
to  the  various  applications. 


222 


Table  2 
Selection  of  the  Proper  Lamp  for  Sign 


and  Display  Lighting 


FOR  DISTRICTS  OF  HIGU  CIRCULATION 


Small 
Exposed-lamp 
Sign s,25  feet  or 
less  from  ground 
Exposed-  lamp 

25  to75feef 

from  ground 
Lar^e  or  Roof 
Exposed-  lamp 
Si^ns,  75  feet 
or  higher 

Enclosed 
Lamp 


SURROUNDING    ILLUMINATION 


1A2DA-B 


BRIGHT 

50  WATT 

WHITE 

MAZDA 


l§ 
- 


25WATT 


25  WATT 
iplM-5 

ittlA'R' 


50WATT    50WATT 

MAZDA  MAZDA-C 
DAYLIGHT    CLEAR 


:  -r 


-       AMAZDA-C  MAZDA  HAID/VC 

*V«v    fUvt  t/-ur    TJCAO      HAVJ  I/5UT    Pi  CAD 


: 


II  jp|  HI  '.•- 


DAYLIGHT  CLEAR 


:;.v-w,rT'--75WATT  75\^TT 
,    IHPA-C  MAZDA  MAZDA-C 
;HT   CLEAR    DAYLIGHT    CLEAR 


Marquees 

Building 

Outline 

Lighting 


WATT 


50  WATT 

WHITE 

MAZDA 


75  WATT 
WHJTE 
MAZDA 


BLUE 


50WATT  50WATT  75WATT 

MAZDA  WHITE  WHITE 
IT  MAZDA  MAZDA 


TOR  DISTRICTS  OF  LOV  CIRCULATION 


Small 
Exposed -I  amp 
Si3rns,25feetor| 
less  from 
Exposed- lam 

Si^ns 

25  to  75  feet 
from  ground 

Lar^e  or  Poof 
E.xposed-lamp 
Si°ns,75feet 
or  higher 

Enclosed 
Lamp 
Si9,ns 


Marquees 

Building 

Outline 

Lighting 


CLEAR 


25  WATT 
MAZDA- B 
DIFFUSING 


DA-B 

R 


E5WATT 

NAZDA- B 
CLEAR 


mWmr 

^DA:': 

^•l:ioH::\ 


CL&AR 


50WATT     50WATT 
MAZDA     MAZDA-C 
DAYLIGHT     CLEAR 


;  5  WATT 

mm  ri 


50WATT 

NAZDA 
DAYLIGHT 


50WATT 

MAZDA-C 
CLEAR 


50WATT 


50WATT 

WHITE 
MAZDA 


BLUE 
MAZDA 

Si 


2§V^TT        50WATT 

MAZDA-B   MAZDA-B 
CLEAR    DIFFUSING 


223 


Fig.  4 — An  Example  of  the  Pattern  of  a  Sign  with  the  Spots 
of  Light  Almost  Touching 

Enclosed  Lamp  Signs 

From  Table  1,  it  will  be  seen  that  10-watt  lamps  spaced  as 
closely  as  mechanical  considerations  will  permit  will  not  provide 
an  unbroken  line  of  light  when  viewed  at  distances  of  less  than 
about  300  feet.  While  illuminated  translucent  letter  signs  do 
not  have  the  brightness  and  sparkle  of  the  exposed  lamp  sign, 
the  smoother,  more  even,  and  clearer-cut  outline  of  the  trans- 
lucent letter  sign  gives  it  a  distinct  advantage  for  the  shorter 
effective  distances. 

The  appearance  of  signs  of  this  type  is  greatly  influenced  by 
the  lamp  spacing  behind  the  letter,  the  depth  of  the  box,  and  the 
color  of  the  interior  surface.  If  the  lamps  are  spaced  too  far 
apart,  the  pattern  will  appear  spotty.  If  they  are  placed  too  far 
inside  the  edge  of  the  pattern,  the  outline  will  be  ragged  and  in- 
distinct. A  6-inch  spacing  from  lamp  to  lamp  and  a  3-inch  spac- 
ing from  lamp  to  projected  edge  of  pattern  will  prove  satisfac- 


Fig.  5. — A  Very  Effective  Exposed  Lamp  Sign 
224 


Fig.  6. — Building  Outline  Lighting  with  Exposed  Lamps 

tory  in  signs  of  ordinary  construction  providing  the  interior 
surfaces  are  finished  in  white. 

For  signs  with  6-inch  letters,  or  larger,  of  uniform  height,  it 
is  preferable  to  use  the  same  number  of  lamps  behind  each  letter. 
The  proper  number  may  be  found  by  determining  the  number  of 
square  inches  contained  in  a  rectangle  outlining  the  letter,  divid- 
ing this  number  by  40,  and  using  the  nearest  whole  number. 
Letters  12  inches  high  and  8  inches  wide,  for  example,  would  re- 
quire two  lamps. 

Suggestions  as  to  the  best  sizes  and  kinds  of  lamps  to  employ 
in  enclosed  lamp  signs  under  various  conditions  of  service  are 
given  in  Table  2. 

Importance  of  Beauty  in  Sign  Displays 

Fully  as  important  as  the  mechanics  of  sign  design  discussed 
above,  are  the  factors  which  affect  the  artistic  appeal  of  the 
display.  The  sign  which  attracts  but  does  not  hold  attention 
is  low  in  advertising  value  no  matter  how  legibly  the  message 
is  displayed.  It  is  through  the  intelligent  use  of  color  and  pro- 
portion, the  grouping  of  lamps,  and  the  control  of  brightness 
that  the  designer  is  able  to  produce  a  result  which  is  effective 
as  an  advertising  medium  and  which  has  the  additional  attri- 
bute of  beauty.  Displays  of  this  type  not  only  build  good-will 

225- 


Fig.  7.— The  Beautiful  Border  Adds  Greatly  to  the 
Effectiveness   of   this    Sign 

for   the   advertiser   but   they   promote   the   development   of   the 
sign  industry  as  well. 

Bulletin  and  Poster  Boards 

In  order  that  bulletin  and  poster  boards  may  be  illuminated 
to  the  best  advantage,  it  is  necessary  that  the  light  sources  be 
concealed  from  the  eye,  that  glare  caused  by  the  direct  reflection 
of  the  lighting  units  from  the  painted  surface  be  minimized,  and 
that  the  illumination  be  fairly  uniform  and  of  an  intensity  high 
enough  to  cause  the  sign  to  stand  out  prominently.  Glare  may 
be  avoided  by  mounting  the  units  so  that  the  light  is  thrown 
upon  the  sign  from  below,  in  which  case,  since  the  angle  of  in- 
cidence is  equal  to  the  angle  of  reflection,  direct  reflection  cannot 
enter  the  eye  of  the  observer  unless  he  is  looking  down  upon 
the  sign  from  above.  This  arrangement  is  shown  diagrammatic- 
ally  in  Fig.  8.  If,  as  is  sometimes  the  case,  the  sign  is  so  lo- 
cated that  the  observer  looks  down  upon  it,  it  is  evident  that 
glare  may  be  avoided  by  reversing  the  arrangement,  that  is,  by 
lighting  the  sign  from  above.  Such  installations  are  applicable 
chiefly  to  signs  which  are  so  situated  that  floodlighting  pro- 
jectors may  be  used  to  project  the  light  from  the  roof  or  windows 
of  a  neighboring  building  upon  the  face  of  the  sign,  for  if  the 
units  were  mounted  close  to  the  sign  in  the  usual  manner,  their 
supports  would  in  most  cases  obstruct  a  view  of  the  sign. 

Another  method  of  mounting  the  units  which  overcomes  a 
large  part  of  the  trouble  from  glare  is  to  mount  them  well 

226 


Lev*], 


Fig.  8. — Location  of  Units  to  Avoid 


Fig.  9  Fig.  10 

The  Higher  the  Unit  is  Mounted  Above  the  Sign,  for  a  Given  Distance 
in  Front  of  the  Sign,  the  Less  will  be  the  Distance  Through  Which 
Glare  will  be  Apparent;  However,  a  Highly  Concentrating  Re- 
flector   Becomes    Essential 

above  the  sign.  If  this  is  done,  the  observer  will  have  to  ap- 
proach the  sign  closely  before  the  glare  is  apparent.  Fig.  9 
shows  that  the  higher  the  unit  is  mounted  above  the  sign  for  a 
given  distance  in  front  of  the  sign  the  less  will  be  the  distance 
through  which  glare  will  be  apparent.  However,  it  will  be  noted 
from  Fig.  10  that  the  higher  the  unit,  the  more  concentrated  the 
distribution  must  be  to  be  effective ;  in  this  case,  raising  the  re- 
flector 4  feet  reduces  the  effective  zone  from  68  degrees  to  29 
degrees. 

There  is  no  moderate  priced  reflector  for  outdoor  service 
at  present  manufactured  which  when  mounted  high  above  and 
close  to  the  sign  will  satisfactorily  illuminate  it  except  at  a  very 
considerable  sacrifice  of  efficiency.  Obviously,  were  such  re- 
flectors to  be  had,  another  difficulty  would  be  experienced  in 
spacing  units  so  as  to  obtain  a  uniform  distribution  lengthwise  of 
the  board. 


227 


With  the  present  reflector  equipment,  the  most  practical 
illumination  of  bulletin  and  poster  boards  is  accomplished  by 
means  of  Mazda  lamps  equipped  with  porcelain-enameled  steel 
angle  reflectors  mounted  in  front  of,  and  somewhat  above,  the 
top  edge  of  the  sign.  Such  reflectors,  if  well  designed,  waste 
little  of  the  light  above  and  below  the  sign,  and  direct  the  beam 
of  maximum  intensity  toward  the  bottom  of  the  sign,  which  is 
important  not  only  because  this  part  of  the  sign  is  farthest  from 
the  light  source  but  also  because  of  the  acute  angle  at  which  the 
rays  strike  this  part  of  the  sign.  They  have  also  the  decided 


Fig.  11 

Two   Groups   of  Well   Designed   Properly   Maintained    Billboards    as 

Found  in    California.     The   lighting   equipment   is    neat   and 

inconspicuous.       Advertising     of     this      character     is 

an  asset  to  the  community 

advantage  of  being  small  in  size  and  light  in  weight,  which  per- 
mits them  to  be  hung  far  enough  out  from  the  sign  to  give  uni- 
formity of  light  distribution  with  little  strain  on  the  mechanical 
supports,  and  with  a  relatively  small  amount  of  shadow  thrown 
upon  the  sign  in  the  daytime.  The  porcelain-enameled  surface  is 
weatherproof,  does  not  collect  dirt  easily,  and  is  readily  cleaned. 
The  data  given  in  Table  3  apply  to  bulletin  and  poster  board 
lighting  under  usual  conditions,  that  is,  for  boards  situated  in 
well  lighted  districts.  Where  the  surrounding  intensities  are 

228 


Table  3 
Specifications  for  Billboard  Illumination 

Height  of  ^—Mounting  Dimensions  of  Lighting  Units— >  Av.  lllumina- 

Board,  Spacing,        Distance  Out,  Distance  Above,  Size  of  Lamp,        tion,  Foot- 

Feet  Feet  Feet  Feet  Watts  Candles 

3-5  541  75  9 

6-8  651  100  9 

9-12  6y2              7                  1  200  10 

13-17  981^  300  11 

18-21  12                 11                   2  500  10 

22-25  16                 15                   2  750  11 

25  20                 18                  2  1000  10 

particularly  high,  larger  units  than  those  specified  should  of 
course  be  employed  in  order  that  the  board  will  be  at  least  as 
brilliant  as  its  surroundings. 

The  tendency  is  to  mount  units  too  close  to  the  board,  causing 
poor  illumination.  The  advantage  gained  in  mounting  the  units 
far  out  from  the  sign  offsets  the  cost  since  the  distances  from 
the  unit  to  the  top  of  the  board  and  from  the  unit  to  the  bottom 
of  the  board  are  more  nearly  equalized,  thus  the  light  is  more 
evenly  distributed,  and  the  highest  intensity  is  directed  toward 
the  bottom  of  the  board  without  the  necessity  of  tilting  the  re- 
flector at  such  an  angle  that  the  top  of  the  board  is  in  shadow. 

In  installing  lighting  equipment  for  a  bulletin  board,  access- 
ibility of  the  units  should  always  be  given  consideration.  The 
units  should  be  so  mounted  that  they  can  be  reached  regard- 
less of  the  weather  conditions  as  by  this  means  much  time  and 
labor  can  be  saved.  The  mounting  should  be  of  such  a  charac- 
ter that  the  supports  will  withstand  any  wind  pressure  that 
tends  to  displace  them  from  their  proper  positions. 

Bulletin  and  poster  boards  located  in  inaccessible  places 
or  at  considerable  distances  from  the  power  supply  are  usually 
illuminated  by  floodlighting  projectors.  These  employ  concen- 
trated filament  lamps  in  properly  designed  reflectors  of  the 
parabolic  type  and  direct  a  concentrated  or  spread  beam,  as 
occasion  demands,  on  the  sign. 

An  interesting  and  effective  innovation  in  bulletin  lighting 
is  the  application  of  color  effects.  Colored  objects  present  dif- 
ferent appearances  when  illuminated  by  various  colors  of  light. 
Red  light  falling  on  a  blue  object  makes  it  appear  black;  green 
light  falling  on  a  yellow  object  makes  it  appear  green.  A  red 
object  on  a  white  background,  if  illuminated  by  red  light,  is 
practically  invisible,  for  both  the  object  and  the  background  are 
equally  luminous.  Similarly,  green  light  would  cause  a  green 

229 


/     BLUE 
ALLEY  BUTTERS 


Fig.  12. — The  Combination  of  Bulletin  Board  and 

Exposed  Lamp  Display  is   New  and   Quite 

Effective 

object  to  blend  with  the  background  and  be  invisible.  It  can 
be  readily  seen  that  by  proper  painting  of  the  sign  and  the 
application  of  suitably  tinted  light,  complete  changes  are  possible 
as  the  light  is  changed  by  means  of  a  flasher. 

Building  Outline  and  Marquee  Lighting 

The  problem  involved  in  this  form  of  electrical  advertising 
is  one  of  good  taste  more  than  of  sign  engineering.  The 
effect  produced  should  be  in  keeping  with  the  character  of  the 
building.  The  garish  effect  which  might  be  desirable  for  an 
amusement  park  would  not  be  in  keeping  with  the  dignity 
of  an  impressive  bank  or  public  building.  The  best  result  can 
be  obtained  only  when  full  co-operation  exists  between  the 
architect  and  the  sign  designer. 

Table  1  shows  the  proper  lamp  spacing  to  be  employed  to 
obtain  unbroken  lines  of  light ;  Table  2  suggests  the  sizes  and 
kinds  of  lamps  suitable  for  outline  and  marquee  lighting. 

Floodlighted  Advertising 

Building  fronts,*  bulletin  and  poster  boards,  and  signs  on 
water  towers  and  chimneys  are  some  of  the  advertisements 
which  may  often  be  floodlighted  advantageously.  To  accom- 
plish this,  projectors  are  used  to  throw  the  light  from  a  distance 


*  See  also  Part  XI,  Flood-Lighting,  page  166. 

230 


IMPROVEMENT  m  AVERAGE  BRIGHTNESS 

No  maintenance  for  16 months, Stamps  only  burning  when  examined 

Dockets  filled  -5 lamps  burning 

Letters  uiped  off  porously)  on  outside  uith a dry  c/oth 

Letters  washed  on  outside  uith  soap  anc/uafer 

Letters  and  box  washed  on  ins/de. 


Five  additional  lamps  (making  tota/ofJO-SOuatt  MAZDA  C  clear 
lamps)  installed  to  make  Itfhtinf  conform  tobestpractic  e. 


IMPROVEMENT  INUNIFORMITYOF  BRIGHTNESS 

After  18  months  without  maintenance.  (3  lamps  only  burning) 

I "RATIO  150  to  1 

I  I 

Noc/eanin.sf-fire  neu  lamps  burning 

RATIO    4-tol 


^  '///////////////////////ZZA T^ATIQ   2tol 

| ' 

^Brightness  of  brightest  areas 
^Brightness  of  darkest  areas 

Fig.   13. — Importance  of  Adequate  Maintenance 

upon  the  surface  to  be  illuminated.  The  number  and  type  of 
projectors  to  be  used  depends  upon  the  size  of  the  advertise- 
ment and  its  position  with  respect  to  the  projectors. 

SIGN  MAINTENANCE 

In  general,  better  advertising  value  over  a  period  of  a  year 
or  more  will  be  obtained  from  a  small  sign  which  is  washed  and 
cleaned  just  as  often  as  the  show  window  is  washed,  and  which 
is  painted  and  has  a  change  of  lamps  say  three  or  four  times  a 
year,  than  will  be  obtained  from  a  sign  twice  the  size  which  is 
neglected  until  it  is  dirty  and  five  or  ten  per  cent  of  the  lamps 
are  burned  out. 

While  the  need  for  adequate  maintenance  exists  for  all  signs, 
it  is  more  important  for  the  small  ones  than  for  the  large  ones, 
and  it  is  especially  needed  for  enclosed  lamp  signs.  In  such 

231 


signs  there  are  three  surfaces  to  be  kept  clean.  One  only  of 
these  is  exposed  to  the  street  dust  but  although  the  others  are 
inside  and  somewhat  protected  they  are  never  washed  by  the 
rain  as  are  the  lamps  in  an  exposed  lamp  sign.  Practically  all 
of  these  signs  have  a  neat  and  clean  appearance  when  new  but 
show  slight  deposits  of  dirt  quickly.  For  this  reason  enclosed 
lamp  signs  should  be  so  constructed  that  the  inside  of  the  letters 
may  be  easily  reached  or,  preferably,  that  the  letters  may  be  re- 
moved and  washed  in  soap  and  water,  not  merely  rubbed  off,  but 
washed  in  the  water  frequently.  Making  box  signs  with  re- 
movable letters  similar  to  theatre  feature  boards  increases  their 
cost  only  20  per  cent  and  makes  it  possible  to  have  a  sign  which 
always  looks  like  new. 

To  evaluate  the  effect  of  cleaning  a  translucent  letter  sign, 
such  a  sign  was  examined  recently.  The  brightness  in  five  posi- 
tions was  measured  both  before  and  after  cleaning,  and  after 
replacing  the  lamps  with  the  proper  number  of  new  ones  of  the 
correct  size.  The  results  are  shown  in  Fig.  13.  The  average 
brightness  of  the  sign  was  increased  twelve  times,  the  ratio 
of  the  brightness  of  the  bright  spots  to  that  of  the  dull  spots  in 
the  sign  was  reduced  from  one  hundred  and  fifty  to  one  to  two 
to  one.  It  is  probably  true  that,  in  these  lower  ranges  the  at- 
tracting power  of  a  sign  is  increased  at  least  in  proportion  to 
that  of  the  average  brightness  and  the  selling  power  inversely 
as  the  variation  in  brightness. 


232 


PART  XVII 

Code  of  Lighting  Factories,  Mills  and 
Other  Work  Places 

Prepared  under  the  direction  of  and  issued  by  the  Illuminating   Engineering 
Society,  New  York,  N.  Y.     Reprinted  through  the  courtesy  of  the  Society. 

INTRODUCTION 

THE  accompanying  Code  of  Lighting  for  factories,  mills  and  other 
work  places  has  been   prepared   and   issued   by  the  Illuminating 
Engineering  Society  in  order  to  make  available  authoritative  infor- 
mation for  legislative  bodies,  factory  boards,  public  service  commissions 
and  others  who  are  interested  in  enactments,  rules  and  regulations  for 
better  lighting.   The  Code  is  intended  also  as  a  guide  for  factory  owners 
and  operators  in  their  efforts  to  improve  lighting  conditions  in   their 
factories. 

Part  I  contains  Rules  arranged  in  convenient  form  for  legal 
enactment  or  governmental  regulations. 

Part  II  contains  a  discussion  of  the  rules  of  Part  I;  that  is,  the 
legal  requirements  which  must  be  met  where  a  Code  is  in  force;  and  also 
suggestions  and  general  information  as  to  desirable  practice  in  factory 
lighting. 

Part  III  takes  up  the  advantages  of  proper  and  adequate  illumina- 
tion, both  natural  and  artificial,  and  discusses  such  lighting  particularly 
from  the  standpoint  of  economics. 

Since  the  first  edition  of  this  Code  was  issued,  a  number  of  the 
states  of  the  Union,  recognizing  the  beneficial  effects  of  adequate  illumina- 
tion on  the  health  and  safety  of  the  employees,  have  adopted  factory 
lighting  codes.  As  a  rule,  these  codes  stipulate  the  minimum  illumination 
permissible  for  different  classes  of  industrial  operations.  They  also  indi- 
cate the  desirable,  as  distinguished  from  the  minimum  illumination  values, 
and  the  kinds  of  lighting  equipment  which  will  avoid  glare  and  give  a 
good  distribution  of  light. 

The  preface  to  the  Wisconsin  Industrial  Lighting  Code  explains 
as  follows  why  the  state  is  concerned  in  the  regulation  of  Factory  Lighting : 

"Insufficient  and  improperly  applied  illumination  is  a  prolific  cause  of  industrial 
accidents.  In  the  past  few  years  numerous  investigators,  studying  the  cause  of  accidents, 
have  found  that  the  accident  rate  in  plants  with  poor  lighting  is  higher  than  similar 

233 


plants  which  are  well  illuminated.    Factories  which  have  installed  improved  lighting, 
have  experienced  reductions  in  their  accidents  which  are  very  gratifying. 

Of  even  greater  importance,  poor  lighting  impairs  vision.  Because  diminution 
of  eyesight  from  this  cause  is  gradual,  it  may  take  the  individual  years  to  become 
aware  of  it.  This  makes  it  all  the  more  important  to  guard  against  the  insidious  effects 
of  dim  illumination;  of  glaring  light  sources  shining  in  the  eyes;  of  flickering  light;  of 
sharp  shadows;  of  glare  reflected  from  polished  parts  of  the  work.  To  conserve  the 
eyesight  of  the  working  class  is  a  distinct  economic  gain  to  the  state,  but  regardless 
of  that,  humanitarian  considerations  demand  it. 

Finally,  inadequate  illumination  decreases  the  production  of  the  industries 
of  the  state,  and  to  that  extent  the  wealth  of  its  people.  Factory  managers,  who  have 
installed  improved  illumination,  are  unanimous  in  the  conviction  that  better  lighting 
increases  production  and  decreases  spoilage." 

Mr.  R.  E.  Simpson  of  the  Travelers  Insurance  Company  is 
authority  for  the  statement  that  during  the  year  1919  there  were  more 
than  2,000,000  industrial  accidents  causing  loss  of  time;  of  this  number 
25,000  were  fatal.  The  following  extract  from  an  article  in  the  Travelers 
Standard  by  Mr.  Simpson  gives  some  interesting  data  on  the  relation 
between  lighting  and  safety: 

"There  is  some  foundation  for  assuming  that  18  per  cent  of  our 
industrial  accidents  are  due  to  the  defects  in  lighting  installations.  On 
that  basis  the  services  of  108,000  men  for  one  year  are  lost  annually 
because  the  illumination  provided  is  not  adequate  for  the  safety  of  the 
workmen.  That  this  condition  could  exist  year  after  year  is  all  the  more 
reprehensible,  because  of  the  fact  that  the  remedy  is  so  easily  applied, 
and  has  beneficial  results  in  many  ways  other  than  the  safety  involved. 
Accidents  caused  by  carelessness,  inattention  or  ignorance  can  be  elimi- 
nated only  by  a  long  continued,  painstaking,  educational  campajgn,  often 
involving  a  change  in  long  established  habits.  Elimination  of  accidents, 
due  to  inadequate  or  improper  lighting  is  simply  a  matter  of  purchasing 
the  proper  equipment,  and  installing  it  under  competent  directions.  In 
fact,  it  seems  proper  to  include  illumination  in  the  list  of  mechanical 
safeguards,  for  the  reason  that  the  lamps  and  reflectors  provide  a  guard; 
illumination  points  out  the  hazards  just  as  effectively  as  a  railing  points 
out  the  danger  of,  and  provides  protection  against,  the  hazard  of  a 
revolving  flywheel." 


234 


PART  I. 

RULES. 

Note:  Attention  is  called  to  the  fact  that  the  requirements  given  in  the  Rules  are  mini- 
mum specifications  and  are  not  to  be  interpreted  as  sufficient  to  insure  good 
lighting.  See  PART  II — Suggestions  and  General  Information. 

General  Requirement.  Traversed  spaces,  during  the  time  of  use, 
and  work  in  process,  shall  be  supplied  with  light  in  accordance  with  the 
following  rules: 

Rule  1.  Illumination  Required.  The  illumination  maintained 
shall  be  not  less  than  given  in  the  following  table: 

TABLE  I. 

Minimum 
foot-candles 
On  the  space 

or 
at  the  work 

(a)  Roadways;   Yard  Thoroughfares 0.02 

(b)  Storage  Spaces;  aisles  and  passageways  in  workrooms  excepting 

exits  and  passages  leading  thereto 0.25 

(c)  Where  Discrimination  of  Detail  Is  Not  Essential 0.5 

Spaces,  such  as: — Hallways,  stairways;  exits,  and  passages  lead- 
ing thereto;  toilet  rooms;  elevator  cars  and  landings. 
Work,  such  as: — Handling  material  of  a  coarse  nature;  grinding 
clay  products;   rough  sorting;   coal  and  ash  handling;    foundry 
charging. 

(d)  Where  Slight  Discrimination  of  Detail  Is  Essential 1 

Spaces,  such  as: — Stairways,  passageways  and  other  locations 
where  there  are  exposed  moving  machines,  hot  pipes,  or  live 
electrical  parts. 

Work,  such  as: — Rough  machining,  rough  assembling;  rough 
bench  work;  rough  forging;  grain  milling. 

(e)  Where  Moderate  Discrimination  of  Detail  Is  Essential 2 

Work,  such  as: — Machining;  assembly  work ;  bench  work;  fine 
core  making  in  foundries;  cigarette  rolling. 

(f )  Where  Close  Discrimination  of  Detail  Is  Essential ; . . .  3 

Work,  such  as: — Fine  lathe  work;  pattern  making;  tool  making; 
weaving  light  colored  silk  or  woolen  textiles ;  office  work ;  account- 
ing; typewriting. 

(g)  Where  Discrimination  of  Minute  Detail  Is  Essential 5 

Work,  such  as: — Watchmaking;  engraving;  drafting;  sewing 
dark  colored  material. 


235 


Rule  2.  Avoidance  of  Glare :  Diffusion  and  Distribution  of 
Light.  Lighting  whether  natural  or  artificial  shall  be  such  as  to  avoid 
glare,  objectionable  shadows  and  extreme  contrasts,  and  to  provide  a 
good  distribution  of  light;  in  artificial  lighting  systems,  lamps  shall  be  so 
installed  in  regard  to  height,  location,  spacing,  and  reflectors,  shades  or 
other  suitable  accessories,  as  to  accomplish  these  objects. 

Bare  light  sources,  such  as  exposed  lamp  filaments  or  gas  mantles 
located  within  the  ordinary  field  of  the  worker's  vision,  are  presumptive 
evidence  of  glare. 

For  a  specification  of  definite  requirements  under  this  rule,  reference 
should  be  had  to  Tables  III,  IV,  V  and  VI  in  Part  II. 

Rule  3.  Exit  and  Emergency  Lighting.  The  lighting  to  be 
provided  under  Rule  1  in  all  stairways  and  exits  of  factories  and  in  the 
passageways  appurtenant  thereto  shall  be  supplied  so  as  not  to  be  subject 
to  failure  because  of  the  failure  of  the  room  or  work  space  lighting  from 
internal  causes,  and  preferably  from  an  independent  connection  extending 
back  to  the  main  service  entrance  for  the  building.  In  case  of  unusual 
danger  which  may  exist  on  account  of  type  of  building,  nature  of  the 
work,  crowded  conditions  or  lack  of  suitable  exit  space,  an  independent 
service  shall  be  ensured  by  connecting  to  a  separate  source  of  supply 
without  or  within  the  building. 


236 


PART  II. 

SUGGESTIONS  AND  GENERAL  INFORMATION 
Notes  on  Rule  1 — Illumination  Required. 

THE  illumination  values  given  in  Table  I  are  minimum  requirements 
dictated  from  the  viewpoint  of  safety.  Table  II  given  below  is 
intended  to  indicate  the  order  of  illumination  values  that  are  con- 
sidered desirable  for  different  classes  of  work.  Letters  in  parentheses 
following  foot-candle  values,  refer  to  the  corresponding  sub-divisions  of 
Table  I.  Persons  of  advanced  years  and  those  with  defective  eyes  require 
more  light  than  those  having  perfect  vision.  The  foot-candles  in  good 
lighting  practice  are  as  a  rule  several  times  those  specified  as  minimum 
requirements.  A  range  of  foot-candle  values  is  given  in  Table  II  for  each 
group  of  operations ;  in  modern  practice  it  will  usually  be  found  desirable 
to  select  values  in  or  even  beyond  the  upper  portion  of  the  range. 

TABLE  II. 

APPROXIMATE  FOOT-CANDLES  IN  GOOD  LIGHTING 
PRACTICE  ON  THE  SPACE  OR  AT  THE  WORK 

Ho  TO  %  FOOT-CANDLES  (a) 

Roadways  and  Yard  Thoroughfares. 

1  TO  2  FOOT-CANDLES  (b) 

Storage  Spaces:  aisles  and  passageways  in  work  rooms,  excepting  exits  and  passages 
leading  thereto. 

2  TO  5  FOOT-CANDLES  (c)  and  (d) 

Auditoriums  and  Assembly  Rooms. 

Assembling:  rough. 

Boilers,  Engine  Rooms  and  Power  Houses:  boilers,  coal  and  ash  handlings,  storage- 
battery  rooms,  auxiliary  equipment,  oil  switches  and  transformers. 

Chemical  Works:  hand  furnaces,  boiling  tanks,  stationary  driers,  stationary  or  gravity 
crystallizing,  mechanical  furnaces,  generators  and  stills,  mechanical  driers, 
evaporators,  filtration,  mechanical  crystallizing,  bleaching. 

Clay  Products:  grinding,  filter  presses,  kiln  rooms,  molding,  pressing,  cleaning  and 
trimming. 

Elevator,  Cars  and  Landings:   (freight  and  passenger). 

Forge  Shops  and  Welding:   rough  forging. 

Foundries:  charging  floor,  tumbling,  cleaning,  pouring  and  shaking  out. 

Glass  Works:  mix  and  furnace  rooms,  casting. 

Hallways:  stairways,  exits  and  passages  leading  thereto. 

237 


Leather  Manufacturing:  vats,  cleaning,  tanning  and  stretching. 

Locker  Rooms. 

Meat  Packing:  slaughtering. 

Machine  Shops:  rough  bench  and  machine  work  and  rough  assembling. 

Milling  and  Grain  Foods:   cleaning,  grinding  or  rolling. 

Packing:  rough. 

Paint  Shops:   dripping,  spraying,  firing. 

Paper  Manufacturing:  beaters,  machine  grinding. 

Plating. 

Receiving  and  Shipping. 

Soap  Manufacturing:   kettle  houses,  cutting,  soap  chip  and  powder. 

Steel  and  Iron  Mills:    charging  and  casting  floors,  muck  and  heavy  rolling,  shearing 
(rough  by  gage),  pickling  and  cleaning,  soaking  pits  and  reheating  furnaces. 

Store  Rooms  and  Stock  Rooms:  rough. 

Textile  Mills:    (Cotton)  opening  and  lapping,  carding,  drawing- frame,  roving,  dyeing; 
(Woolen)  carding,  picking,  washing  and  combing. 

Toilet  and  Wash  Rooms. 

Woodworking:  rough  sawing  and  rough  bench  work. 


5  TO  10  FOOT-CANDLES  (e)  and  (f) 

Assembling:  medium,  fine. 

Chemical  Works:  tanks  for  cooking,  extractors,  percolators,  nitrators,  electrolytic  cells. 

Clay  Products:  enameling,   coloring  and  glazing. 

Cloth  Products:  light  goods. 

Electric  Manufacturing:   storage  battery,  molding  of  grids,  coil  and  armature  winding, 
mica  working,  insulating  processes. 

Engine  Rooms  and  Power  Houses:    switchboards,  engines,  generators,  blowers,  com- 
pressors. 

Forge  Shops  and  Welding:   fine  forging  and  welding. 

Foundries:  fine  molding  and  core  making. 

Glass   Works:    grinding,  glass  blowing  machines,  cutting,  polishing,  inspecting. 

Glove  Manufacturing:  light  goods:  sorting,  stitching,  trimming  and  inspecting. 

Hat  Manufacturing:   dyeing,  stiffening,  braiding,  cleaning  and  refining,  forming,  sizing, 
pouncing,  flanging,  finishing  and  ironing;   sewing:   light  goods. 

Ice  Making:  engine  and  compressor  rooms. 
Inspecting:   rough,  medium. 

238 


Leather  Manufacturing:  cutting,  fleshing  and  stuffing,   finishing  and  scarfing. 

Leather  Working:  pressing  and  winding,  grading,  matching,  cutting,  scarfing;  sewing: 
light  goods. 

Machine  Shops:  medium  bench  and  machine  work,  ordinary  automatic  machines, 
rough  grinding,  medium  buffing  and  polishing. 

Meat  Packing:  cleaning,  cutting,  cooking,  grinding,  canning,  and  packing. 
Milling  and  Grain  Foods:  baking,  roasting. 
Office:   private,  general 
Packing:   medium,  fine. 

Paint  Shops:  rubbing,  ordinary  hand  painting  and  finishing,  fine  hand  painting  and 
finishing. 

Paper  Manufacturing:   calendering,  finishing,  cutting  and  trimming. 
Polishing  and  Burnishing. 

Printing  Industries:  matrixing  and  casting,  miscellaneous  machines,  presses,  proof- 
reading, lithographing,  electrotyping. 

Rubber  Manufacturing  and  Products:  calenders,  compounding  mills,  fabric  preparation, 
stock  cutting,  tubing  machines,  solid-tire  operations,  mechanical  goods  building, 
vulcanizing,  bead  building,  pneumatic  tire  building  and  finishing,  inner-tube  opera- 
tion, mechanical  goods  trimming,  treading. 

School:  class  room,  study  room,  library. 

Sheet  Metal  Works:  miscellaneous  machines,  bench  work,  punches,  presses,  shears, 
stamps,  welders,  spinning. 

Shoe  Manufacturing:  hand  turning,  miscellaneous  bench  and  machine  work,  inspecting 
and  sorting  raw  material,  cutting,  lasting  and  welding:  light  goods. 

Soap  Manufacturing:   stamping,  wrapping  and  packing,  filling  and  packing  powder. 

Steel  and  Iron  Mills:  bar  sheet  and  wire  products;  automatic  machines,  rod  light  and 
cold  rolling,  wire  drawing,  shearing  (fine  by  line). 

Store  Rooms  and  Stock  Rooms:   medium,    fine. 
Structural  Steel  Fabrication. 

Textile  Mills:  (Cotton)  spooling,  spinning,  drawing  in,  warping,  weaving,  quilling, 
inspecting,  knitting,  slashing.  (Silk)  winding,  throwing,  dyeing,  quilling,  warping, 
weaving  and  finishing.  (Woolen)  twisting,  and  dyeing;  drawing  in,  warping; 
weaving;  knitting  machines:  light  goods. 

Wood  Working:  sizing,  planing,  standing,  machine  and  bench  work,  gluing,  veneering, 
cooperage,  finishing. 


10  TO  20  FOOT-CANDLES  AND  ABOVE  (g) 

Assembling:  extra  fine. 

Cloth  Products:  dark  goods. 

Glass  Works:  glass  cutting  (cut  glass) ;  inspecting,  fine. 

Glove  Manufacturing:  dark  goods:   sorting,  stitching,  trimming,  and  inspecting. 

Hat  Manufacturing:  sewing:   dark  goods. 

Inspecting:  fine. 

Jewelry  and  Watch  Manufacturing:  engraving,  stone  setting,  fine  repairing. 

Leather  Working:  grading,  matching,  cutting,  scarfing,  sewing:   dark  goods. 

Machine  Shops:   fine  bench  and  machine  work,  fine  automatic  machines,  fine  grinding, 
fine  buffing  and  polishing. 

Office:  drafting  room. 

Paint  Shops:  extra  fine  hand  painting  and  finishing  (automobile  bodies,  piano  cases,  etc.). 

Printing  Industries:  linotype,  monotype,  typesetting,  imposing  stone,  engraving. 

Shoe  Manufacturing:    inspecting  and  sorting  raw  material,  cutting,  stitching:    dark 
goods. 

Textile  Mills:  woolens;   weaving:  dark  goods. 

In  Tables  I  and  II  the  illumination  requirements  are  specified  in 
foot-candles.  The  term  "foot-candle"  may  be  explained  by  saying  that 
it  represents  the  illumination  on  a  surface  one  foot  distant  from  a  standard 
candle;  two  foot-candles  would  represent  the  illumination  supplied  by 
two  candles  at  the  same  distance,  etc.  In  this  illustration  it  is  assumed, 
of  course,  that  in  each  case  the  surface  is  perpendicular  to  the  direction  of 
the  rays  of  light  falling  upon  it. 

At  first  sight  it  might  appear  from  Tables  I  and  II  that  there  is  a 
sharp  line  of  demarcation  between  those  operations  for  which  one  foot- 
candle  is  specified  and  those  which  require  two  foot-candles,  etc.  In 
reality  no  such  well  defined  classification  exists  and  in  applying  the 
Tables  the  inspector  will  find  that  in  certain  cases,  because  of  the  degree 
of  fineness  of  the  work  carried  on  in  a  particular  plant,  one  grade  higher 
or  one  grade  lower  than  that  which  first  suggests  itself  may  be  a  more 
reasonable  requirement. 

Again,  it  should  not  be  overlooked  that  there  are  occasional  opera- 
tions which  need  to  be  performed  practically  without  light,  such  as 


240 


photographic  and  photometric  processes  in  dark  rooms.  Again,  there  are 
some  operations  which  are  best  observed  by  their  own  light,  as  in  certain 
parts  of  the  process  of  working  with  glass.  In  all  cases  in  which  work 
must  be  performed  under  very  low  illumination,  special  precaution  should 
be  taken  to  safeguard  the  workers  from  accident. 

In  applying  the  illumination  requirements  as  given  in  Tables  I 
and  II  the  foot-candles  specified  should  not  be  construed  as  referring  only 
to  a  horizontal  plane ;  the  illumination  should  be  measured  on  whatever 
plane  the  work  or  operation  is  carried  on,  whether  it  is  on  a  horizontal, 
vertical  or  intermediate  plane.  With  most  artificial  lighting  systems  the 
foot-candles  measured  on  a  vertical  plane  are  about  one-half  the  illumina- 
tion in  the  same  location  measured  on  a  horizontal  plane.  Attention  is 
also  called  to  the  fact  that  the  values  in  Table  I  are  minimum  values; 
that  is,  they  apply  to  measurements  of  the  lighting  system  in  ordinary 
operation,  not  simply  when  the  lamps  and  reflectors  are  new  and  clean. 

Natural  Lighting — The  foot-candle  values  given  apply  to  natural 
as  well  as  to  artificial  lighting.  In  practice  it  will  be  found  that  the  natural 
illumination  on  clear  days  is  frequently  many  times  these  figures;  in  fact, 
an  illumination  of  a  hundred  foot-candles  can  be  found  in  almost  any 
shop  if  measurements  are  taken  near  the  window,  and  very  often  mechanics 
find  it  worth  while  to  avail  themselves  of  this  illumination  by  walking 
over  to  the  window  whenever  extremely  accurate  measurements  are  to  be 
made.  In  this  connection  it  is  of  interest  to  note  that  the  range  of  illumina- 
tion under  which  the  eye  can  function  with  some  degree  of  success  is 
extremely  wide,  varying  from  a  few  hundred ths  of  a  foot-candle  in  the 
moonlight  up  to  as  much  as  ten  thousand  foot-candles  out  in  the  sunlight 
on  a  clear  day.  However,  wide  extremes  in  illumination  are  ordinarily 
not  conducive  to  best  vision. 

Most  factory  owners  are  particularly  interested  in  making  the 
best  possible  use  of  their  daylight  facilities,  so  as  to  render  useful  and 
valuable  all  parts  of  the  floor  space;  and  also,  to  shorten  the  periods 
when  artificial  lighting  is  needed.  The  saw-tooth  sky- windows  of  modern 
factory  construction  (Fig.  i),  permit  of  an  adequate  and  nearly  uniform 


241 


daylight  illumination  of  the  entire  floor  area,  and  are  desirable  when 
practicable.  When  rooms  are  illuminated  through  side  windows,  it  is  often 
difficult,  or  impossible,  satisfactorily  to  light  all  parts  of  the  floor  space,  or 
to  furnish  adequate  illumination  to  some  of  the  workers  without  fur- 
nishing too  much  to  others,  or  without  subjecting  the  latter  to  objection- 
able glare.  In  some  cases  the  use  of  prismatic  glass  which  redirects  the 
rays  of  light  so  as  to  admit  more  daylight  into  the  room,  especially  into 
the  parts  of  the  room  remote  from  the  windows,  is  worth  while.  As  a 
rule  it  is  better  to  confine  the  prismatic  glass  to  the  upper  sash  of  a 
window,  as  its  use  in  the  lower  sash  is  likely  to  cause  objectionable  glare; 
moreover  it  cuts  off  all  view  of  out  of  doors. 

Windows  should  be  equipped  with  adjustable  devices  so  that  the 
illumination  may  be  accommodated  to  changing  exterior  conditions. 
Translucent  window  shades  of  light  tones  constitute  the  most  important  of 
these  devices.  Window  shades  or  other  daylight  adjusting  devices  should 
not  be  left  to  the  mercy  of  those  workers  who  may  be  nearest  the  windows, 
but  should  be  controlled  by  the  room  foreman.  He  should  readjust  the 
window  equipment  for  the  varying  daylight  conditions  and  he  should, 
also,  decide  when  the  use  of  artificial  light  to  make  up  for  a  deficiency  in 
daylight  in  any  location,  is  permissible. 

Because  of  the  time  required  for  the  adaptation  of  the  eye  to  its 
surroundings  special  danger  is  present  when  one  steps  from  outdoor 
sunlight  into  a  dimly  lighted  storage  space;  for  example,  a  passageway 
connecting  two  well-lighted  areas  must  be  well  illuminated.  Again,  where 
the  eye  has  been  afforded  the  advantages  of  a  high  level  of  illumination 
throughout  the  day  and  artificial  light  is  turned  on  to  reinforce  the  failing 
natural  light,  a  higher  total  illumination  is  ordinarily  needed  than  at 
night  under  artificial  lighting  alone. 

Maintenance  of  Illumination — The  proper  and  adequate  main- 
tenance of  equipment  for  both  natural  and  artificial  lighting  is  essential. 
Systems  which  are  adequate  when  first  installed  will  soon  deteriorate 
unless  properly  maintained.  The  factory  owner  should  establish  a  regular, 
definite  system  of  maintenance  so  as  to  insure  that  sky  windows,  side 
windows,  lamps  and  accessories  are  at  all  times  kept  clean,  in  proper 


242 


Fig.  1. — Saw-tooth  roof  construction,  with  glass  facing  the  north  sky,  usually  results  in  well 
diffused  daylight  illumination. 


Final  Intensity 


CASE  I 
Occasional  Maintenance 


CASE  II 
No  Maintenance 


Periodic  but  Inade- 
quate Maintenance 


Fig.  2. — Chart  showing  the  importance  of  prompt  renewal  of  burned  out  lamps  and  systematic 
cleaning  of  the  lighting  equipment.  These  particular  tests  were  on  semi-indirect  and 
indirect  lighting  systems. 


243 


adjustment  and  in  good  repair.  Means  should  be  provided  for  easy 
access  to  all  lighting  units  by  the  employee  in  charge  of  their  maintenance. 
Walls  and  ceilings  should  be  repainted,  preferably  in  light  tones,  at  regular 
intervals,  particularly  where,  as  in  indirect  systems  of  lighting,  a  large 
part  of  the  illumination  comes  from  the  ceiling.  It  should  be  kept  in  mind 
that  the  illumination  requirements  given  in  the  tables  apply  to  the 
lighting  equipment  under  adverse  operating  conditions,  not  simply  new 
and  clean  as  when  first  installed. 

Figs.  2  and  3  show  the  very  considerable  loss  in  illumination  which 
results  from  the  collection  of  dirt  on  lamps  and  lighting  fixtures.  To  insure 
that  a  given  level  of  illumination  will  be  maintained  even  where  condi- 
tions are  favorable,  it  is  necessary  to  design  the  system  to  give  initially 
at  least  25  per  cent  more  light  than  the  required  minimum.  In  locations 
where  the  dirt  will  collect  rapidly  and  where  adequate  maintenance  is  not 
provided,  the  initial  value  should  be  at  least  50  per  cent  above  the 
minimum  requirement,  and  it  is  evident  from  a  study  of  the  charts  that 
even  this  allowance  may  prove  insufficient. 

Especially  in  connection  with  the  maintenance  of  lighting  systems 
attention  is  called  to  the  desirability  of  having  available  in  the  factory 
some  instrument  with  which  the  foot-candles  of  illumination  received  at 
any  point  can  actually  be  measured.  There  are  a  number  of  such  instru- 
ments on  the  market,  some  of  which,  in  the  hands  of  experienced  men, 
are  capable  of  a  high  degree  of  accuracy.  One  instrument,  the  foot-candle 
meter  (Fig.  4),  is  not  designed  for  precise  measurements,  but  nevertheless, 
has  a  considerable  field  of  usefulness  because  its  determinations  are  easily 
made  and  are  accurate  enough  for  many  practical  purposes.  The  foot- 
candle  meter  is  small,  light  in  weight,  and  does  not  require  technical 
training  for  its  operation ;  foot-candle  illumination  is  read  directly  from 
the  scale  without  computation  or  adjustment.  In  one  large  establishment 
where  the  superintendent  uses  a  foot-candle  meter  systematically  as  a 
check  on  his  maintenance  department,  readings  of  illumination  are  taken 
at  regular  intervals  at  fixed  stations  throughout  the  plant.  These 
readings  are  recorded  in  such  a  way  that  the  successive  readings  are 
readily  comparable.  When  any  inconsistency  appears  in  the  records  an 


244 


MAINTENANCE     RECORD 


'kllu^t 


JAN  FE8  MAR  APR  MAY 


«.«jwwW*iW 


J  t  s  tf'mfis 


z  a.  2.  (t  a.  z.  a.  a. 


JL/N  |JUL 


^^ 


Fig.  3. — Lighting  Maintenance  Record. 


Fis.  4. — A  survey  of  actual  lighting  conditions  can  readily  be  made  with  the  foot-candle  meter. 
This  instrument  is  very  useful  in  "checking  up"  a  lighting  system  to  see  that  it  is  being 
properly  maintained. 


245 


investigation  is  made  and  the  remedy  applied.  The  illumination  in  that 
establishment  is  never  allowed  to  fall  below  6  foot-candles  without 
immediate  correction.  By  measuring  light  actually  delivered  t©  the  work 
the  foot-candle  meter  automatically  reveals  the  combined  effect  of  all 
possible  causes  of  depreciation.  Ignorance  of  the  magnitude  of  deprecia- 
tion has  often  been  the  cause  of  inadequate  maintenance.  Soap  and 
water  cost  less  than  gas  and  electrical  energy. 

Locating  Switches  and  Controls — The  switches  which  turn  on  and 
off  the  light  in  the  entrances  and  halls  of  a  building  should  be  located 
near  the  points  of  entrance.  Likewise  switches  which  control  at  least  one 
circuit  of  lamps  in  a  room  should  be  located  near  the  principal  points  of 
entrance  to  that  room. 

In  locating  switches  or  control  devices  in  factory  and  mill  aisles, 
care  should  be  exercised  to  arrange  them  systematically;  that  is,  on 
columns  situated  on  the  same  side  of  the  aisle  and  on  the  same  relative 
side  of  each  column.  This  plan  materially  simplifies  the  finding  of  switches 
or  control  devices,  by  those  responsible  for  turning  on  and  off  the  light. 

Control  Parallel  to  Windows — The  light  from  the  lamps  most 
distant  from  the  windows  will  usually  be  required  at  times  when  the 
natural  light  near  the  windows  is  entirely  adequate,  thus  making  it  advan- 
tageous to  arrange  the  groups  of  lamps  in  circuits  parallel  to  the  windows. 
The  advantage  of  this  method  is  further  apparent  when  it  is  considered 
that  if  the  lamps  are  controlled  in  rows  perpendicular  to  the  windows,  all 
lamps  in  a  row  will  necessarily  be  on  at  one  time,  while  a  portion  only 
may  be  required. 

Notes  on  Rule  2 — Avoidance  of  Glare. 

Glare  may  be  defined  as  any  brightness  within  the  field  of  vision 
of  such  a  character  as  to  cause  discomfort,  annoyance,  interference  with 
vision,  or  eye  fatigue.  Always  a  hindrance  to  vision,  it  often,  like  smoke 
from  a  chimney,  represents  a  positive  waste  of  energy  as  well.  It  is  one 
of  the  most  common  and  serious  faults  of  lighting  installations;  the  Code 
properly  requires  the  shading  of  lamps  in  industrial  plants  to  guard 
against  glare. 

Glare  is  Objectionable  because  (1)  when  continued  it  tends  to  injure 

246 


the  eye  and  to  disturb  the  nervous  system;  (2)  it  causes  discomfort  and 
fatigue  and  thus  reduces  the  efficiency  of  the  worker;  and  (3)  it  interferes 
with  clear  vision,  and  thus  reduces  the  efficiency  and  in  many  cases, 
increases  the  risk  of  accident  or  injury  to  the  worker.  From  both  a 
humanitarian  and  a  business  viewpoint,  the  owner  or  operator  of  a  factory 
should  be  interested  in  avoiding  glare,  whether  caused  by  daylight  or  by 
artificial  light.  On  the  other  hand,  in  interpreting  and  enforcing  the  glare 
rule  the  inspector  is  not  expected  to  insist  upon  what  he  may  believe  to  be 
desirable  practice  in  the  given  case;  his  duty  is  only  to  insure  the  absence 
of  a  condition  which  is  prejudicial  either  to  the  health  or  to  the  safety  of 
the  worker. 

If  a  simple  instrument  were  available  for  measuring  glare  the  task 
of  the  inspector  would  be  comparatively  easy.  However,  there  are  so 
many  factors  entering  into  the  situation  that  it  has  not  been  found 
practicable  to  develop  any  instrument  which  will  properly  evaluate  them 
all.  To  arrive  at  an  intelligent  judgment  in  any  given  case,  therefore, 
the  inspector  must  be  reasonably  familiar  with  the  principal  factors  in  or 
causes  of  glare. 

CA  USES  OF  GLARE— There  are  five  principal  causes  of  glare: 

1.  Brightness  of  Source — The  light  source  may  be  too  bright; 
that  is,  it  may  give  off  too  high  a  candlepower  per  square  inch  of  area. 

A  glance  at  the  sun  proves  that  an  extremely  bright  light  source  within  the  field 
of  vision  is  capable  of  producing  acute  discomfort.  Light  sources  of  far  lower  brightness 
than  the  sun,  such  for  example,  as  the  filament  of  an  incandescent  electric  lamp  or  the 
incandescent  mantle  of  a  gas  lamp,  may  also  cause  discomfort,  although  the  annoying 
effect  is  usually  not  quite  so  marked. 

2.  Total  Volume  of  Light — The  light  source  may  be  too  powerful 
for  comfort;   that  is,  it  may  give  off  too  great  a  total  candlepower  in  the 
direction  of  the  eye. 

Too  frequently  glare  is  assumed  to  be  entirely  a  question  of  the  brightness  of  the 
light  source;  of  equal  importance  is  the  question  of  its  total  candle-power.  Experience 
has  shown  that  a  500-watt  lamp  in  a  10-in.  opal  globe,  or  a  mercury-vapor  lamp  of  an 
equivalent  light  output,  hung  7  or  8  feet  above  the  floor  and  a  similar  distance  ahead  of 
the  observer  will  prove  quite  as  glaring  as  the  exposed  filament  of  a  50- watt  incandescent 


247 


lamp  in  the  same  location.  The  brightness  of  the  opal  globe  unit  is  only  a  few  times  that 
of  a  candle  flame,  but  its  total  candle-power  and  consequently  the  quantity  of  light  which 
reaches  the  eye  is  altogether  too  great,  so  that  its  effect  is  worse  than  that  of  the  bare 
filament  of  lower  candle-power,  although  the  latter  may  have  a  brightness  as  high  as 
3000  candle-power  per  square  inch.  An  unshaded  window  often  causes  glare,  due,  of 
course,  to  the  large  volume  of  light  rather  than  to  the  high  brightness  of  the  sky. 

3.  Location  in  the  Field  of  View — A  given  light  source  may  be 
located  at  too  short  a  distance  from  the  eye,  or  it  may  lie  too  near  the 
center  of  the  field  of  vision,  for  comfort;  that  is,  within  too  small  an  angle 
from  the  ordinary  line  of  sight. 

The  500-watt  opal  globe  unit  discussed  in  the  previous  illustration  would  seldom 
cause  discomfort  if  placed,  say  80  feet  away  from  the  observer,  for  at  this  distance  the 
total  quantity  of  light  entering  the  eye  would  be  only  one  one-hundredth  of  that  received 
at  8  ft.  Again,  the  same  light  source  would  probably  be  found  quite  unobjectionable 
at  a  distance  of  8  ft.  from  the  eye  provided  this  distance  was  obtained  by  locating  the 
lamp  4  ft.  ahead  of  the  observer  and  7  ft.  above  the  eye  level;  in  this  case  the  lamp 
would  scarcely  be  within  the  ordinary  field  of  view. 

The  natural  position  of  the  eye  during  intervals  of  rest  from  any  kind  of  work 
is  generally  in  the  horizontal  direction,  and  it  is  desirable  that  during  such  periods  the 
worker  should  be  freed  from  the  annoyance  caused  by  glare.  Glare  is  the  more  objec- 
tionable the  more  nearly  the  light  source  approaches  the  direct  line  of  sight.  While  at 
work  the  eye  is  usually  directed  either  horizontally  or  at  an  angle  below  the  horizontal. 
Glaring  objects  at  or  below  the  horizontal  should  especially  be  prohibited.  The  best 
way  to  remove  light  sources  out  of  the  direct  line  of  vision  is  to  locate  them  well  up  toward 
the  ceiling.  Local  lamps,  that  is,  lamps  placed  close  to  the  work,  if  used  at  all,  must  be 
particularly  well  screened. 

4.  Contrast  with  Background — The  contrast  may  be  too  great 
between  the  light  source  and  its  darker  surroundings. 

It  is  a  common  experience  that  a  lamp  viewed  against  a  dark  wall  is  far  more 
trying  to  the  eyes  than  when  its  surroundings  appear  relatively  light.  A  light  background 
requires,  first:  that  the  surface  should  be  painted  in  a  color  which  will  reflect  a  con- 
siderable portion  of  the  light  which  strikes  it,  and  second :  that  the  system  of  illumination 
employed  should  be  such  as  to  direct  some  light  upon  the  background.  In  many  cases 
the  ceiling  appears  almost  black  under  artificial  light  simply  because  no  light  reaches 
it.  With  daylight,  on  the  other  hand,  the  walls  of  a  room  are  often  so  well  illuminated 
that  they  appear  brighter  than  the  work  itself  and  this,  also,  is  a  condition  which  is 
not  conducive  to  good  vision.  In  general,  a  light  tone  for  ceilings  and  high  side  walls 
and  a  paint  of  medium  reflecting  power  for  the  lower  side  walls  will  ordinarily  be  found 
most  satisfactory  under  both  artificial  and  natural  lighting. 

248 


d 

SBJ 


III 
l-l 

=  ° 


Ill 


111 

C*"  ° 
5    •  <n 

el  a 


SB! 
lei 


III 


ts-d 

i     <U 


Til 


249 


Where  strictly  local  lighting  systems  are  employed,  that  is,  where  individual 
lamps  are  supplied  for  all  benches  and  machines,  and  no  overhead  lighting  is  added,  the 
resulting  contrasts  in  illumination  will  usually  be  found  so  harsh  as  to  be  objectionable 
even  though  the  lamps  themselves  are  well  shielded.  The  eyes  of  the  workman  looking 
up  from  his  brightly  lighted  machine  or  bench  are  not  adapted  for  vision  at  low  illumina- 
tions; hence,  if  adjacent  objects  and  aisles  are  only  dimly  lighted,  he  will  be  compelled 
either  to  grope  about,  losing  time  and  risking  accident,  or  to  wait  until  his  eyes  have 
become  adapted  to  the  low  illumination.  Glancing  back  at  his  work,  he  again  loses  time 
while  his  eyes  adjust  themselves  to  the  increased  amount  of  light  which  reaches  them. 
If  long  continued,  this  condition  leads  to  fatigue,  as  well  as  to  interference  with  vision, 
and  to  accidents.  In  other  words,  where  local  lamps  are  employed,  there  should  also 
be  a  system  of  overhead  lighting  which  will  provide  a  sufficient  illumination  of  all  sur- 
rounding areas  to  avoid  such  undesirable  contrasts. 

5 .  Time  of  Exposure — The  time  of  exposure  may  be  too  great ,  that 
is,  the  eye  may  be  subjected  to  the  strain  caused  by  a  light  source  of  given 
strength  within  the  field  of  vision  for  too  long  a  time. 

Where  an  operator  is  seated  and  his  field  of  vision  is  fixed  for  several  hours  at  a 
time,  light  sources  of  lower  brightness  and  lower  candlepower  are  required  than  where 
the  operator  stands  at  his  work  and  shifts  his  position  and  direction  of  view  from  time 
to  time.  In  the  first  case  the  image  of  the  light  source  is  focused  on  one  part  of  the  retina 
for  considerable  periods  of  time  and  is  obviously  more  likely  to  cause  discomfort  and 
eye  strain  than  when  present  for  short  periods  only.  Those  who  are  forced  to  work  all 
day  at  desks  facing  the  windows  are  particularly  likely  to  suffer  from  this  form  of  glare. 

RATING  LIGHT  SOURCES  FROM  THE  GLARE  STAND- 
POINT— It  is  evident  that  the  first  two  factors  mentioned  as  causes  of 
glare,  namely,  excessive  brightness  and  excessive  candlepower,  concern 
the  light  source  itself,  the  third  factor  concerns  its  location  in  the  field  of 
view ;  and  the  fourth  and  fifth  depend  upon  the  conditions  of  its  use. 

In  Table  III  a  means  of  rating  light  sources  (into  Grades  I  to  X) 
has  been  provided  which  takes  into  account  both  their  brightness  and  their 
candlepower.  Light  sources  in  Grades  I  and  II  may  be  termed  soft  or 
well  diffused;  those  in  Grades  VIII,  IX  and  X  are  harsh  and  likely  to 
cause  glare.  It  is  seen  from  Table  III  that  a  light  source  of  high  intrinsic 
brightness  but  of  low  candlepower, — for  example,  one  that  would  be 

250 


classified  under  the  fifth  line  of  the  first  column  (less  than  20  cp. — and 
100  to  1000  cp.  per  sq.  in.)  has  the  same  rating,  Grade  V,  as  a  source  of 
lower  brightness  but  of  greater  total  candlepower,  (2-5  cp.  per  sq.  in.  and 
500  total  cp.)  which  falls  in  the  second  line  of  the  fifth  column. 


TABLE  III. 

CLASSIFICATION  OF  LIGHT  SOURCES  FROM  THE 
STANDPOINT  OF  GLARE 

Grade  I  indicates  sources  of  maximum  softness. 
Grade  X  indicates  sources  of  maximum  harshness. 


MAXIMUM  VISIBLE 
BRIGHTNESS 

TOTAL  CANDLE  POWER  IN  DIRECTION 
OF  EYE. 

(Apparent  candles 
per  sq.  in.) 

Less 
than 
20 

20 
to 
50 

50 
to 
150 

150 
to 
500 

500 
to 
2000 

Grade 

Grade 

Grade 

Grade 

Grade 

Less  than  2 

I 

I 

II 

II 

III 

2  to  5 

II 

II 

III 

IV 

V 

5  to  20 

II 

III 

IV 

VI 

VII 

20  to  100 

IV 

V 

VI 

VII 

VIII 

100  to  1000 

V 

VI 

VII 

VIII 

IX 

1000  and  up 

VI 

VII 

VIII 

IX 

X 

In  accordance  with  the  plan  of  Table  III  measurements  of  bright- 
ness and  candlepower  have  been  made  on  a  number  of  light  sources  found 
in  every  day  practice,  both  natural  and  artificial,  and  grades  have  been 
assigned  to  them  as  shown  in  Table  IV.  While  engaged  in  his  work,  the 
inspector  will,  of  course,  find  other  light  sources  in  use  which  are  not 
included  in  the  Table ;  however,  from  those  which  are  given  he  should  be 
able  to  estimate  closely  in  what  grades  the  others  should  be  placed.  In 
cases  of  doubt,  it  is,  of  course,  possible  to  have  actual  measurements 
made  to  determine  both  the  brightness  of  the  lighting  unit  and  its  total 
candlepower.  The  unit  can  then  be  rated  in  accordance  with  Table  III. 


TABLE   IV. 

SPECIFIC   CLASSIFICATION   OF   LIGHT  SOURCES  FROM   THE 
STANDPOINT   OF   GLARE   AS   DERIVED    FROM    TABLE   III 


NATURAL  LIGHT  SOURCES 

(As  seen  through  windows  or  skylights) 

Grade 


Sun 

Very  Bright  Sky 

Dull  Sky 

Sun  Showing  on  Prism  Glass 


OPEN  GAS  FLAMES 


X 

V 

III 

IX 

II 


INCANDESCENT  MANTLE  GAS  LAMPS 


Mantles 
Consuming 
2-5  cu.  ft. 
per  hr. 

Mantles 
Consuming 
5-8  cu.  ft. 
per  hr. 

Large  Sin- 
gle Mantle 
or  Cluster 
8-12  cu.    ft. 
per  hr. 

Large    Sin- 
gle   Mantle 
or  Cluster 
12-20cu.ft. 
per  hr. 

Cluster  or 
High    Pres- 
sure Lamp 
consuming 
above  20cu. 
ft.  per  hr. 

Clear  Glassware 

Grade 
V 

Grade 
VI 

Grade 
VII 

Grade 
VIII 

Grade 
IX 

Frosted  Globes 

III 

IV 

6-in.  Opal  Globe 
8-in.  Opal  Globe* 
10-in.  Opal  Globe* 
12-in.  Opal  Globe* 

II 

I 

III 
II 

IV-VI 
III-V 

V-VII 

VI-VIII 

Dome  Reflector 
Mantle  Visible 
Mantle  not  Visible 

V 
I 

VI 
II 

VII 
III 

VIII 
IV 

IX 
IV 

Bowl  Reflector 
Mantle  Visible 
Mantle  not  Visible 

V 
II 

VI 
II 

VII 

III 

VIII 
V 

IX 
V 

Totally  Indirect* 
Semi-Indirect  Bowls* 

I-II 
II-III 

II 
II-IV 

III 
1  1  1-  VI 

*Where  a  range  is  given  the  best  grade,  that  is  the  lowest,  applies  to  globes  that  are  evenly  luminous, 
and  the  poorest  to  globes  which  have  a  decidedly  bright  spot  in  the  center. 


252 


TABLE  IV.— Continued 

ARC  LAMPS 


Enclosed  arcs,  clear  globes 
Flame  arc,  clear  globes 
Flame  arc,  opal  globes 


MERCURY  VAPOR  TUBES 


Grade 

IX 

X 

VII-VIII 

VI 


CARBON    AND    METALLIZED    FILAMENT    INCANDESCENT    LAMPS 

8  c.  p.  V 

16  c.  p.  V 

32  c.  p.  VI 

TUNGSTEN  FILAMENT  INCANDESCENT  LAMPS 


WATTS 

10-25 

40-60 

75-100 

150-200 

300 

500-1000 

Bare  Lamps 

Grade 
VI 

Grade 
VII 

Grade 
VIII 

Grade 
IX 

Grade 
IX 

Grade 
X 

Frosted  Lamps  or  Frosted 
Globes 

II 

III 

VI 

VII 

VIII 

8-in.  Opal  Globes* 
12-in.  Opal  Globes* 
16-in.  Opal  Globes* 

I 

I-II 

II-IV 

II-III 

IV-VI 
II-V 
II-V 

IV-VI 
IV-VI 

VII-VIII 
V-VII 

Flat  Reflectors  —  Filament 
Visible 

VI 

VII 

VIII 

IX 

IX 

X 

Dome  Reflectors  —  Steel  or 
Dense  Glass 
Filament  visible  from 
working  position 
Filament  not  vis.  from 
working  position 

VI 

I 

VII 

I 

VIII 

III 

IX 

III 

IX 
IV 

X 
VI 

Bowl  Reflectors  —  Steel  or 
Dense  Glass 
Filament  visible  from 
working  position 
Filament  not  visible  from 
working  position 

VI 

II 

VII 

II 

VIII 

III 

IX 
IV 

IX 
VI 

X 
VII 

Dome  Reflectors  —  Bowl- 
Enameled  Lamps 

IV 

V 

VI 

VI 

Semi-Enclosing  Units* 
Totally  Indirect  Lighting* 
Semi-Indirect  Bowls* 

III-IV 

I-II 
I-III 

IV-VI 

I-II 
II-III 

IV-  VI  I 

II 

II-IV 

VI-VIII 

III 

1  1  1-  VI 

*Where  a  range  is  given,  the  best  grade,  that  is  the  lowest,  applies  to  globes  that  are  evenly  luminous, 
and  the  poorest  to  globes  which  have  a  decidedly  bright  spot  in  the  center. 


253 


TABLE  V. 


CHART  OF  THE  FIELD  OF  VIEW 

Classification  of  Position  of  Light    Source  Which  Takes  into  Account    the  Distance 
from  the  Eye  and  the  Angle  of  the  line  of  Vision.     (See  Fig.  6). 


Height  above 
Floor  in  Feet 

1 

HORIZONTAL  DISTANCE  OF  LIGHT 
FROM  OBSERVER  IN  FEET 
2     3     4     6     8     10  12  16  20  25  30  35  40 

SOURCE 

50  60  &  up 

6  .  5  or  less 
6.5  -  7 

7-8 

A* 
G 
G 

A* 
E 
G 

A 
D 
F 

A 
C 
E 

A 

C 
D 

A  A 
B  B 
D  C 

A  A  A 
B  B  B 
C  C  C 

A  A 
B  B 
C  C 

B    B 
B    B 
C    C 

B    B 
B    C 
C    C 

8-9 
9  -  10 
10-  11 

G 
G 
G 

G 
G 

c; 

G 
G 
G 

F 
G 
G 

F 

F 
G 

E  D 
F  E 
F  F 

D  C  C 
E  E  D 
FEE 

C  C 
D  D 
D  D 

C    C 
D    D 
D    D 

C    D 
D    D 
D    D 

11  -  12 
12-  13 
13  -  14 

G 
G 
G 

c; 

G 
G 

G 
G 
G 

G 
G 
G 

G 
G 
G 

G  F 
G  G 

F  F  F 
G  F  F 

E  E 
E  E 
F  F 

D    D 
E    E 
E    E 

D    D 
E    E 
E    E 

14-  15 
15-  16 
16-  17 

G 
G 
G 

G 

G 
G 

G 
G 
G 

G 
G 
G 

G 
G 
G 

G  G 
G  G 
G  G 

G  G  F 
G  G  F 
G  G  G 

F  F 
F  F 
F  F 

F    E 
F    E 
F    F 

WWW 
WWW 

17  -  18 
18  -  19 
19  -  20  and  up 

G 
G 
G 

G 
G 
G 

c; 

G 
G 

G 
G 
G 

G 
G 
G 

G  G 
G  G 
G  G 

G  G  G 
G  G  G 
G  G  G 

G  G 
G  G 
G  G 

F    F 
G    G 
G    G 

F    F 
G    F 
G    G 

*Classified  as  A  unless  light  source  is  so  nearly  above  the  head  of  operator 
of  field  of  view  in  which  case  classify  as  E, 


to  be  quite  outside 


Fig.  6 — Diagram  illustrating  typical  position  given- 


254 


TABLE   VI. 

SHOWING  LIMITING  GRADES  OF  LIGHT  SOURCES 
PERMISSIBLE  FOR  VARIOUS  CONDITIONS 


Classifica- 
tion of 
Position. 

Space  or  work  to  be  lighted. 

Roadways  and 
Yard  Thorough- 
fares 

Storage  spaces, 
Aisles,  Stair- 
ways, Handling 
Coarse  Material 

Ordinary 
Manufacturing 
Operations  f 

Offices  and 
Drafting  Work 
and  Certain   Mfg. 
Operations* 

A 
B 
C 
D 
E 
F 
G 

Limiting 
Grade 
VI 
VII 
VIII 
IX 
IX 
X 
X 

Limiting 
Grade 
V 
VI 
VII 
VIII 
IX 
X 
X 

Limiting 
Grade 
III 
V 
VI 
VII 
VIII 
IX 
X 

Limiting 
Grade 
II 
IV 
V 
VI 
VII 
VIII 
X 

BACKGROUND 

Where  the  background  and  the  surroundings  are  very  dark  in  tone, 
a  light  source  of  one  grade  softer  than  that  specified  in  Table  VI  may  be 
required.  Where  the  background  and  surroundings  are  very  light  in  tone 
one  grade  more  harsh  than  that  specified  in  the  table  may  sometimes  be 
permitted. 


fFor  the  present  the  limits  set  in  this  table  cannot  be  rigidly  applied  to  portable 
lamps  used  for  temporary  work  such  as  setting  up  machines,  repairing  automobiles,  etc. 

Those  operations  in  which  workers  are  seated  facing  in  one  direction  for  long 
periods  of  time. 


E.YE:  LEVEL  SFT. 
ABOVE:  FLOOR 


he  chart  of  the  field  of  view,  see  Table  V. 


255 


From  a  study  of  Table  IV  it  will  be  observed  that  Incandescent 
lamps  equipped  with  reflectors  which  do  not  completely  hide  the  light 
source  have  been  assigned  to  the  same  grade  as  the  corresponding  sizes 
of  bare  lamps.  It  is  true  that  the  addition  of  a  reflector  somewhat 
increases  the  total  candlepower  in  the  direction  of  the  eye  and  therefore  the 
argument  might  be  advanced  that  a  100-watt  lamp  with  a  flat  reflector 
should  be  classified  in  Grade  IX  whereas  the  bare  lamp  is  Grade  VIII. 
On  the  other  hand,  from  the  standpoint  of  glare,  the  effect  of  the  light 
background  furnished  by  the  reflector  at  least  compensates  for  the 
increased  candlepower  *which  it  gives;  the  rating  is  therefore  kept  at 
Grade  VIII. 

Charting  the  Field  of  View — It  has  already  been  pointed  out  that 
the  distance  between  a  light  source  and  the  eye,  and  its  angle  to  the  line 
of  vision  have  much  to  do  with  determining  how  bright  a  light  source 
may  be  used  without  discomfort.  In  Table  V,  which  is  a  chart  of  the  field 
of  view,  the  possible  locations  of  light  sources  are  classified  in  seven 
groups,  A  to  G  inclusive,  depending  upon  their  distance  from  the  eye  and 
their  proximity  to  the  line  of  vision.  Light  sources  in  positions  designated 
A,  B  or  C,  are  close  to  the  eye  or  close  to  the  line  of  vision ;  hence  they  are 
most  likely  to  be  the  cause  of  discomfort,  and  the  greatest  care  must  be 
exercised  in  their  selection.  In  positions  F  and  G,  on  the  other  hand,  the 
use  of  relatively  bright  sources  is  much  less  harmful. 

Limiting  Grades  for  Specific  Installations — Table  VI  shows  the 
harshest  grade  of  light  source  which  should  be  permitted  within  the  field 
of  vision  for  fixed  conditions  as  to  location  of  lamp,  brightness  of  back- 
ground, and  character  of  work  performed. 

The  grades  named  in  Table  VI  are  definitely  limiting  values  and 
in  each  case  the  use  of  softer  light  sources  is  to  be  recommended;  that  is, 
where  Grade  IV  is  permitted,  the  installation  of  a  lighting  unit  of  Grade  I! 
or  of  Grade  III  will  be  conducive  to  better  results  as  regards  both 
accuracy  of  vision  and  eye  comfort. 

From  Table  IV  the  majority  of  bare  incandescent  lamps  are  seen 
to  have  a  relatively  poor  rating;  that  is,  most  of  them  fall  in  Grades  VI J 
to  IX,  and  it  is  evident  from  Table  VI  that  Grades  VII  to  IX  are  never  te 

256 


Figs.  7  and  8. — Adjoining  rooms  in  the  same  factory.  The  upper  figure  illustrates  a  strictly 
local  lighting  system  of  the  poorer  sort.  The  lower  figure  illustrates  a  lighting  system 
consisting  of  150-watt  bowl  enameled  lamps  equipped  with  dome  reflectors  spaced 
10  feet  apart;  the  average  illumination  is  9  foot-candles. 


257 


be  permitted  in  work  rooms  in  positions  A,  B  or  C.  That  is,  the  use  of 
bare  incandescent  lamps  is  prohibited  in  working  areas  except  when  they 
are  located  at  considerable  heights  above  the  floor  or  when  they  are  so 
placed  as  to  be  out  of  the  field  of  vision.  At  the  present  time  it  will  be 
found  necessary  from  a  practicable  standpoint  to  delay  the  strict  enforce- 
ment of  this  provision  in  a  very  few  instances,  particularly  in  the  case  of 
extension  cord  lamps  used  in  temporary  work,  such  as  in  setting  up 
machinery  and  in  repairing  automobiles,  etc. 

It  will  be  noted  from  Table  IV  that  the  sources  of  natural  light, 
side  and  ceiling  windows,  usually  fall  in  Grade  IV.  This  means  (see  Table 
VI)  that  no  mandatory  rules  are  established  as  to  the  use  of  shades, 
awnings,  etc.,  except  in  those  cases  where  the  sky  is  visible  through 
portions  of  the  sash  in  position  A,  that  is,  less  than  6.5  ft.  above  the 
floor,  or  where  the  sun  itself  comes  within  the  range  of  vision. 

-  However,  Grade  II  is  the  limiting  value  for  light  sources  less  than 
6.5  ft.  high,  in  offices,  and  other  locations  where  the  workers  are  seated 
facing  in  one  direction  for  considerable  periods  of  time.  Hence,  in  these 
cases,  to  comply  with  the  Table,  the  work  must  be  so  arranged  that  the 
employees  are  not  required  to  face  windows  where  the  sky  is  visible 
through  the  lower  sash;  that  is,  less  than  6.5  ft.  above  the  floor. 

Prism  glass  when  so  located  as  to  catch  the  sun's  rays  ordinarily 
has  a  very  much  poorer  rating  than  clear  glass;  hence,  where  it  is  used 
the  installation  of  window  shades  or  curtains  should  ordinarily  be 
required. 

The  question  naturally  arises  why,  if  glare  is  so  objectionable, 
should  not  all  sources  capable  of  producing  glare  be  prohibited  everywhere. 
The  answer  is  that  to  attain  a  maximum  softness  of  light  sometimes 
entails  a  sacrifice  in  efficiency  and  an  increase  in  operating  expense.  If  a 
worker  chooses  unnecessarily  to  gaze  directly  upward  at  bright  skylight 
or  at  an  artificial  lighting  unit  so  located  that  it  is  not  a  factor  in  glare 
under  ordinary  circumstances,  it  is  scarcely  within  the  province  of  a  code 
of  lighting  to  protect  him  from  the  consequences. 


Fig.  9. — Glaring  light  from  unshaded  local  lamp  whicn  is  a  menace  to  saitty  and  to  vision  and 
Is  one  of  the  evils  which  the  Lighting  Code  is  expected  to  eliminate. 


Fig.  10 — Lighting  an  office  by  means  of  indirect  units.     Illumination  approximately  6  foot- 
candles. 


259 


How  to  Use  Tables  IV,  V  and  VI — To  determine  whether  a  given 
lighting  installation  is  within  the  glare  limits  specified,  proceed  as  follows: 

(1)  Select  what  appears  to  be  the  most  glaring  light  source 
within  the  field  of  view  of  any  of  the  employees  when  at  work.    Measure 
the  height  of  that  light  source  above  the  floor  and  its  horizontal  distance 
from  the  worker. 

(2)  With  the  height  and  distance  find  in  Table  V  how  this  loca- 
tion in  the  field  of  view  is  classified,  (Position  A,  B  or  C,  etc.). 

(3)  With  the  classification  of  the  position  fixed  from  (2)  deter- 
mine from  the  proper  column  of  Table  VI  the  harshest  grade  of  light 
source  ordinarily  permissible  for  this  location. 

(4)  If  surroundings  are  very  light  or  very  dark,  apply  a  correc- 
tion of  one  grade  (plus  or  minus)  to  the  value  found  in  (3). 

(5)  From  Table  IV  find  the  classification  of  the  light  source  in 
use  and  compare  with  (4).    (If  the  particular  source  is  not  listed,  its  grade 
may  be  estimated  or  may  be  determined  by  actual  photometric  measure- 
ments.) 

Glare  by  Reflection — Another  way  in  which  glare  is  produced  is  by 
the  reflection  of  light  from  polished  surfaces  in  the  field  of  vision.  The 
difficulty  experienced  in  protecting  the  eyes  from  this  kind  of  glare  is 
sometimes  very  great.  The  brightness  of  the  image  on  the  working  surface 
is,  of  course,  proportional  to  the  brightness  of  the  light  source  above  it, 
and  hence,  one  way  in  which  to  minimize  this  effect  is  to  diffuse  the 
downward  light;  that  is,  to  use  a  bowl-frosted,  or  bowl-enameled  lamp 
or  an  enclosing  fixture,  or  to  employ  semi-indirect  or  totally  indirect 
lighting  fixtures.  In  some  cases  the  light  source  can  be  so  located  that 
its  reflection  is  directed  away  from,  rather  than  towards,  the  eyes  of  the 
workers.  The  avoidance  of  highly  polished  surfaces  in  the  line  of  vision 
is  another  good  way  to  minimize  reflected  glare. 

There  are  some  instances,  on  the  other  hand,  where  sharp  shadows 
and  specular  reflection  from  the  materials  worked  upon  actually  assist 
vision.  For  example  in  sewing  on  dark  goods  the  thread  is  much  more 
easily  distinguished  when  illumination  is  secured  from  a  concentrated 
light  source,  such  as  a  brilliant  lamp  filament,  which  casts  sharp  shadows 
and  gives  rise  to  a  distinct  glint  from  each  thread.  However,  in  these 

260 


Fig.  11. — Drafting  room  lighting  using  dense  semi-indirect  units  and  200-watt  lamps.  The 
glazed  or  shiny  ceiling  will  not  increase  useful  illumination  and  is  frequently  a  source 
of  glare. 


Pig.  12. — A  yard  lighting  installation  consisting  of  150-watt  lamps  in  shallow  bowl  reflectors, 
mounted  20  ft.  from  the  ground.  The  units  in  each  row  are  spaced  60  ft.  apart,  and 
the  two  rows  are  30  ft.  apart. 

26l 


cases  the  light  source  must  be  particularly  well  shielded  from  the  eyes 
of  the  worker. 

Notes  on  Rule  3 — Exit  and  Emergency  Lighting 

The  employer  is  to  be  held  responsible  for  the  proper  lighting  of 
passageways,  stairways  and  exits,  in  so  far  as  his  premises  are  concerned; 
which  means  such  parts  of  buildings,  floors  or  rooms  as  are  controlled 
by  the  employer,  including  entrances  thereto,  but  excluding  hallways, 
passageways  and  stairways  giving  access  to  other  floors,  or  to  spaces  on 
the  same  floor,  and  used  in  common  by  the  tenants  of  the  building.  These 
latter  shall  be  lighted  by  the  party  or  parties  in  control  of  the  building,  in 
accordance  with  the  Code,  and  the  following  provisions  and  interpreta- 
tions thereof: 

"Exit  and  Emergency  Light-Sources"  are  to  be  understood  as 
those  artificial  illuminants  which  are  necessary  only  to  make  clear  to  the 
occupants  or  employees  the  regular  places  of  exit,  or  to  enable  them  to 
pass  to  and  along  safe  exits  with  reasonable  speed  and  assurance  of 
footing.  Such  lighting  is  never  assumed  as  being  necessarily  sufficient 
for  the  proper  performance  of  regular  working  operations. 

The  circuits  for  exit  and  emergency  electric  lamps  should  be  wired 
to  be  independent  of  the  working  lamps,  back  at  least  as  far  as  the  branch 
panel  or  distributing  board,  and  should  be  separately  fused,  so  that  any 
failure  of  the  regular  working  lamps  through  causes  arising  within  that 
working  space  will  not  also  cause  failure  of  the  exit,  stairway,  or  passage- 
way lamps. 

No  fuses  smaller  than  those  of  the  emergency  branch  circuits 
shall  be  used  back  of  (that  is,  on  transformer,  meter  or  generator  side  of) 
such  circuits,  and  no  power  machinery,  portable  extension  cords  or  con- 
venience outlets  shall  be  on  such  emergency  circuits. 

The  "main  service  entrance"  may  be  interpreted  to  mean  the 
entrance  point  (meter  or  distributing  panel)  of  lighting  feeders  for  the 
building,  floor,  loft  or  particular  space  in  question.  In  gas  lighting,  it  may 
be  considered  to  be  the  main  gas  feeder  for  the  building,  or  the  main  gas 
riser  for  the  floor  or  loft  in  question.  Where  several  factory  spaces  are 
grouped  in  the  same  building,  each  with  its  own  exit  or  exits,  the  emergency 
electric  circuits  for  any  one  space  are  not  required  to  run  to  the  main  build - 

262 


Fig.  13 — Lighting  of  steel  rolls.     Illumination  provided  by  five  mantle  inclosed  gas  arc  lamps, 
equipped  with  opaque  reflectors. 


Fig.  14 — Shirtwaist  factory,  sewing  machine  lighting.  Illumination  provided  by  single  mantle 
gas  lamps,  equipped  with  prismatic  reflectors.  Lamps  spaced  9  feet  apart  with  a  clearance 
of  5  feet  above  working  plane. 


263 


ing  panel  board  or  main  switch  nor  are  the  emergency  gas  pipes  expected 
to  extend  to  the  main  gas  meter  nor  to  the  building  feeder  from  the  street 
main,  except  as  explained  below. 

Under  specially  dangerous  conditions,  where  in  the  opinion  of  the 
recognized  authorities  the  failure  of  the  main  and  entire  regular  lighting 
supply  would  leave  the  employees  without  assured  means  of  seeing  the 
outgoing  passageways,  the  exit  and  emergency  lamps  should  be  fed  from 
an  entirely  separate  source  of  energy,  such  as  a  storage  battery,  or,  in 
case  the  regular  lighting  system  is  electric,  from  gas  or  other  reasonably 
dependable  illuminant.  Under  normal  conditions,  however,  the  phrase 
''separate  supply"  shall,  in  electric  service,  be  interpreted  to  mean  a 
separate  branch  circuit  which  will  afford  lighting  as  long  as  transformers, 
generators  or  main  lighting  feeders  are  intact;  and  in  gas  service,  inter- 
preted to  mean  branch  piping  extending  back  to  a  sufficiently  large 
feeder  to  insure  a  gas  supply  unless  stoppage  occurs  near  or  outside  of 
the  main  gas  meter. 

As  indicated  in  the  general  requirements  under  Part  I  of  this 
Code,  the  exit  and  emergency  lamps  should  be  lighted  whenever  artificial 
lighting  is  required  in  the  work  spaces. 

It  is  the  obvious  intent  of  Rule  III  to  insure  reduction  of  accident 
"hazard,  and  inasmuch  as  this  end  is  as  beneficial  to  the  industrial  operator 
or  owner  as  to  the  State,  the  detailed  interpretations  of  this  order,  for 
the  various  and  sundry  types  and  situations  of  working  spaces,  must  be 
reached  through  mutual  co-operation  of  the  owner  and  the  State  authorities. 


264 


PART  III. 

ADVANTAGES  OF  GOOD  ILLUMINATION. 

WHILE  the  advisability  of  good  natural  and  artificial  illumination 
is  so  evident  that  a  list  of  its  effects  may  seem  commonplace, 
these  effects  are  of  such  importance  in  their  relation  to  factory 
management  that  they  are  worthy  of  careful  attention.    The  effects  of 
good  illumination,  both  natural  and  artificial,  and  of  bright  and  cheerful 
interior  surroundings,  include  the  following: 

1.  Reduction  of  accidents. 

2.  Greater   accuracy   in    workmanship,    resulting   in    improved 
quality  of  goods. 

3.  Increased  production  for  the  same  labor  cost. 

4.  Less  eye  strain. 

5.  Greater  contentment  of  the  workmen. 

6.  More  order  and  neatness  in  the  plant. 

7.  Supervision  of  the  men  made  easier. 

While  it  is  difficult  to  place  a  definite  money  value  on  the  savings 
effected  in  increased  production  and  improved  quality,  by  good  illumina- 
tion, it  by  no  means  follows  that  such  savings  are  insignificant  or  unsub- 
stantial. The  factory  owner  who  ignores  them  neglects  his  own  interests. 
Other  items  in  the  foregoing  list,  even  more  difficult  to  value  definitely,  are 
none  the  less  real;  taken  together,  they  constitute  a  powerful  argument 
in  favor  of  the  best  available  illumination  in  the  factory. 

The  following  estimate,  conservatively  based  on  practical  con- 
ditions, gives  an  idea  of  the  relative  costs  of  good  illumination  by  artificial 
means,  and  of  labor,  in  the  factory. 

Assume  that  the  lamps  are  so  spaced  that  one  100-watt  incan- 
descent electric  lamp  will  take  care  of  one  operator ;  that  in  this  particular 
case  the  lamp  burns  on  the  average  two  hours  per  day,  three  hundred 
days  per  year ;  that  the  life  of  the  lamp  is  one  thousand  burning  hours ; 
and  that  the  operator  works  eight  hours  per  day,  300  days  per  year. 


265 


Investment: 

Cost  of  lamp  (list  price) .'....'  $1 . 10 

Cost  of  enameled  steel  reflector  (list  price) 2 . 50 

Cost  of  wiring  per  outlet 8 . 00 

Total  Investment $11.60 

Cost  of  Operating  per  Annum: 

Interest  on  Investment,  $11.60  at  6% $0. 70 

Depreciation  on  reflector  and  wiring  at  12  ;X% 1 .31 

Renewaloflamp  ^^  x$1.10 0.66 

1UUU 

Cleaning,  at  3c.  per  cleaning,  two  per  month 0.72 

Energy  at  5c.  per  kw-h 3 . 00 

Total  Annual  Cost  of  Maintaining  Good  Illumination: 

Per  man  per  year $6.39 

Cost  of  Labor:  Annual  Wages  per  Man  per  year 

Eight  hours  at  45c.  per  hr. ;   8  x  300  x  $.45 $1080 


If  an  operator,  because  of  the  good  illumination,  saves — in  more 
production,  or  better  quality  of  product — the  equivalent  of  only  three 
minutes  per  day  for  300  days,  he  will  offset  the  annual  cost  of  the  illumina- 
tion. Good  illumination  is,  relatively  speaking,  inexpensive,  and  its 
introduction  and  maintenance  are  good  investments  on  the  part  of  the 
factory  owner. 

These  estimated  figures,  illustrating  the  low  cost  of  good  lighting 
compared  with  the  cost  of  labor,  also  illustrate  how  large  may  be  the 
losses  unconsciously  sustained  by  the  factory  owner  from  the  use  of  a 
poor  lighting  system.  An  operator  losing,  say,  30  minutes  per  day,  loses 
more  than  $60.00  per  year,  or  about  ten  times  the  cost  of  giving  him 
good  illumination. 

The  factory  owner,  when  approached  by  the  gas  or  electric  lamp 
salesman,  should  weigh  carefully  any  argument  in  favor  of  a  change  in 
his  lighting  system  which  is  based  solely  upon  a  resultant  saving  in  energy 
consumption.  The  example  given  above  shows  how  greatly  the  gain  in 
increased  output,  due  to  good  lighting,  overbalances  any  possible  saving 
in  energy  consumption  effected  by  changes  in  the  system  of  illumination. 
If  the  proposed  new  system  sacrifices  anything  in  the  quality  of  illumina- 
tion, or  if  it  merely  substitutes  one  inadequate  system  for  another,  it 
should  be  rejected,  and  the  factory  owner  should  insist  that  if  his  lighting 
installation  is  changed,  the  new  system  must  meet  the  requirements  of 
good  illumination  even  though  this  involves  the  consumption  of  more 

266 


Fig.  15. — A  plant  where  machine  tools  are  manufactured,  using  mercury  vapor  lamps  spaced 
20  feet  apart  at  a  height  of  25  feet  above  the  floor;  approximately  1-watt  per  sq.  ft. 


Fig.  16 — Laundry  lighting — Illumination  provided  by   five   mantle   gas  arc  lamps,   inclosed 
type;  equipped  with  diffusing  glass  globes. 

267 


energy  than  before.  First  a  good  lighting  system,  and  then  as  much 
economy  in  energy  consumption  as  is  consistent  with  the  illumination 
requirements — such  a  policy  is  the  wise  one  for  the  factory  owner. 

Accident  Insurance  Costs 

Compensation  insurance  premiums  for  a  given  plant  are  based  on 
the  amount  of  the  payroll,  and  the  rate  is  determined  by  the  accident 
experience  of  a  given  industry,  modified  by  the  experience  of  the  particular 
plant  under  consideration.  With  a  rate  of  one  per  cent  the  annual 
premium  in  the  case  of  1000  employees  at  an  average  wage  of  $40.00  per 
week  would  be  $20,800. 

An  insurance  carrier  might  pay  the  claims  resulting  from  two 
accidents  per  month  (on  an  average)  in  this  plant,  and  meet  his  own 
overhead  costs,  and  still  have  a  slight  margin  of  profit.  An  experience  of 
three  accidents  per  month,  one-third  of  them  due  to  poor  lighting  (a  not 
unlikely  event),  would  probably  leave  the  insurance  carrier  no  option 
but  to  increase  the  rate,  by  say,  50  per  cent.  The  premium  would  then 
be  $31,200 — an  increase  of  $10,400.  If  the  lighting  costs  only  $3.00  per 
employee  or  $3,000  per  year  total,  the  owner's  annual  expense  for  poor 
illumination  actually  amounts  to  $13,400 — of  which  $10,400  is  required 
by  the  insurance  company  to  meet  accident  claims.  An  expenditure  of 
$6.00  per  year  per  employee  for  lamps  and  energy  might  save  a  large 
portion,  if  not  all,  of  the  latter  amount. 

An  Argument  Supplementary  To  The  Code,  Showing  The  Safety 
Feature  of  Good  Illumination 


10.000 


2.000 


Fig.  17. — Chart  of  the  accidents  occurring  in  a  typical  group  of  industries,  indicating  a  higher 
accident  rate  when  light  is  inadequate. 

268 


INDEX  TO  CONTENTS 


PAGE 

Armories,  Intensity  of  Illumination  Desirable 138 

Armories,  Lighting  of 135 

Art  Galleries    142 

Balance   Coil   in   Single   Phase   Circuit,   Diagram   of 85 

Balancer  Set,  Wiring  Diagram 86 

Banks    152-153 

Bathing  Beaches   189 

Billboards,   Samples  of   Good  Design 223 

Billboard  Illumination,   Specifications   for   Table 231 

Bowling  Alleys   193 

Brightness,  Desirable  Wall 12 

Bulletin  and  Poster  Boards 224 

Business  Street,  Table 208 

Ceilings  and  Walls,  Effect  of  Darkening 200 

Churches,    Evangelical    129 

Church  Lighting,  Feasible  Schemes 126 

Church  Lighting,  General  Requirements 125 

Church  Lighting,  Methods  to  Avoid 126 

Churches,  Lighting  of   Chancel 131 

Churches,  Lighting  of  Choir  Loft 132 

Churches,  Lighting  of  Windows 132 

Churches,    Ritualistic    127 

Churches,    Suggestions    for  Wiring 133 

Code  of  Lighting  Factories,  Mills  and  Other  Works  Places 233 

Coefficient  of   Utilization,   Definition 14 

Coefficient  of  Utilization,  Room  Index,  Tables 36-42 

Color  Matching  and  Color  Quality 54 

Dental  Offices 163 

Depreciated  Lighting  Systems,  How  to  Build  Up,  Diagram 201 

Depreciation    Factor,    Definition 1  ^ 

Depreciation  of  Lighting,  Extent  of 199 

Drafting  Rooms  89  &  96 

Drill  Fields   188 

Electrical    Advertising    219 

Electrical  Advertising,  Growing  Appreciation  of,  Diagram 220 

Electric  Signs,  Distribution  of,  According  to  Classes  of  Users 220 

Electric  Signs,  Legibility  Distance  of  Letters,  Diagram 221 

Entrance    Doorway   Lights 54 

Exit  and  Emergency  Lighting  (Code) 236  &  262 

Factory  Room  Illumination   Design 17-18 

Factories,   Good  and  Bad  Lighting  of,    Tables 73 

Field  of  View  (Code),  Chart  and  Table 254-255 

Flood  Lighting   166 

Flood  Lighting,  Choice  of  Equipment 174 

Flood  Lighting,  Calculation  Data,  Tables 171-174 

Flood   Lighting   Equipment 167-169 

Flood  Lighting,  Foot-candle  Illumination  Recommended 174 

Flood  Lighting,  Illumination  Design 176 

Flood  Lighting,  Location  of  Equipment 172 

Flood  Lighting,  Problems  Worked  Out 179-180 

269 


INDEX  TO  CONTENTS 

PAGE 

Flood  Lighting,  Size  and  Number  of  Units 177 

Foot-candles   for    Commercial   and    Public    Interiors,    Present    Standards, 

Tables    25-31 

Foot-candles,  Definition   14 

Foot-candles  for  Industrial  Interiors,  Present  Standards,  Table 27-31 

Foot-candle  Illumination    14 

Foot-candle  Meter   202 

Glare  69 

Glare,  Avoidance  of  ( Code) 246-248 

Clare,  Causes  of   (Code) 247-248 

Glare,  Classification  of  Light  Sources  (Code),  Table 251 

Glare,  Direct   20 

Glare,    Reflected    (Code) 260 

Good   Illumination,   Advantages   of    (Code) 265 

Good    Lighting    for    General    Conditions,    Approximate    Foot-candles    Re- 
quired (Code) 237-240 

Grocery  Store  Lighting,  Installation  and  Plan 58 

Gymnasium,  General  Lighting  Consideration 138 

Gymnasium,  Exercising  Room 142 

Gymnasium,    Running    Track 141 

Gymnasium,  Shower  and  Locker  Rooms 142 

Highways    216 

Hospitals    154 

Hospital    Corridors    157 

Hospital  Operating  Rooms 158-161 

Hospital   Private   Rooms 157 

Hospitals,  Wiring  and  Signal  Systems 162 

Illumination  for  Color  Matching 8 

Illumination  Design   Data 14 

Illumination,  Foot-candles  for  Stores,  Present  Standards,  Table. 25-31 

Illumination  Fundamentals  5 

Illumination,    Horizontal    Surfaces 11 

Illumination,  Intensities  of  Daylight  in  Foot-candles,  Table 64 

Illumination,   Minimum   Required  in   Foot-candles   for   Various   Locations 

and  Uses  (Code) 235 

Illumination,  Uniformity  of 10 

Illumination  Values   Computed 17  &  44-45 

Illumination,  Vertical  Surfaces 11 

Illumination,  Industrial,  Requirements  for  Good  Results 63 

Industrial   Lighting    63 

Insurance  and  Accident  Costs  (Code) 268 

Interior   Lighting   Systems,   Maintenance  of 100 

Lamps,  Mazda,   115  volt  vs.   130  volt 80 

Lamps,   Mazda,  220-250  volt 80 

Lamps,   Mazda,   Importance  of    Prompt   Renewal   of    Those   Burned   Out 

( Code) ,  Diagram  243 

Lamps,  Mazda,  Proper  Size,  Formula  for  Determining 16 

Lamps,  Mazda,  Two  in  Series  on  220-250  volts 82 

Lamp,  Mazda,  Signs,  Exposed 219 

Libraries    148 

Light,  Amount  of,  for  Various  Purposes 5 

Light,  Color  Quality  of 68 

Light,   Diffusion  of , .  6 

Light  on  Work,  Industrial 63 

270 


INDEX  TO  CONTENTS 

PAGE 

Lighting,  Artificial  Compared  with  Interior  Daylight,  Diagram 66 

Lighting  for   Indoor   Recreations 191 

Lighting  Maintenance  Record,  Method  of  Keeping 202 

Lighting  Systems,  How  to  Restore 206 

Lighting  Units,  Direct,  Semi-enclosing  and  Totally  Enclosing,  Table 23 

Lighting  Units,  Direct,  Spacing  and  Mounting  Height,  Table 23-24 

Lighting  Units,  Enclosing  and  Semi-enclosing  for  Direct  Lighting,  Table. .  34 

Lighting  Units,  Number  Required 15 

Lighting  Units,  Semi-indirect  and  Indirect,  Table 35 

Lighting  Units,  Semi  and  Totally  Indirect,  Table 24 

Lighting  Units,  Type  of,  Selection 15 

Lighting  for  Work  Benches,  Auxiliary 79 

Light  Lost  When  Lamps  Are  Operated  Under  Voltage,  Diagram 200 

Lumen,  Definition 14 

Maintenance  of  Illumination   ( Code) 242 

Mazda  Lamps,  Lumen  Output,  Table 43 

Motor  Cycle  and  Bicycle  Tracks 186 

Motor-Generator  Sets  for  Changing  Voltage 83 

Motor-Generator  Set,  Wiring  Diagram 85 

Museums   147 

Night  Lights,  Protection  Against  Robbery 54 

Office  Buildings 89 

Offices,   Comparison  of  Lighting  Systems 91 

Offices,  Methods  of  Lighting 90 

Offices,  Semi-indirect  Lighting  of 92 

Offices,  Spacing  of  Outlets  for  Lighting 94 

Offices,  Wattage  Required  for  Lighting 

Outdoor  Areas    187 

Outdoor  Sports   182 

Outlets  for  Lights,  Location  of 15 

Outlets  for  Factory  Lighting,  Location  of  Diagrams 73-77 

Outline  and  Marquee  Lighting 230 

Outlying  Districts  and  Alleys 216 

Paintings,  Lighting  of 143 

Painting  Gallery,  Diagram  Showing  Incorrect  Lighting 144 

Pool  and  Billiard  Rooms 191 

Public   Buildings    135 

Residence  Lighting,  Kitchen,   Butler's   Pantry,   Laundry,   Den  or   Sewing 
Room,  Living  Room,  Dining  Room,  Hall,  Reception  Room,  Bedroom, 

Bath  Room,   Porch,  Grounds,  Garage 105-124 

Residence  Lighting,  Systems  of 106 

Residence  Streets   212 

Reflecting  Equipment,  Choice  of 19 

Reflecting  Equipment,  Selection  of,  Tables 21-22 

Reflection,  Specular  70 

Reflectors,  Cleaning  of,  Suggested  Schedules 204 

Reflectors,  Open  Glass,  Direct  Lighting,  Table 33 

Reflectors,  Porcelain  Enamel,  Direct  Lighting 32 

School  Lighting    98 

School  Lighting,  Auxiliary  Outlets 104 

School  Lighting,  Blackboards 100 

School  Lighting,  Comparison  of  Various  Lighting  Systems 100 

271 


INDEX  TO  CONTENTS 


School  Lighting,  Classrooms,  Corridors 102-104 

School  Lighting,  General  Consideration 99 

School  Lighting,  Harmful  Effects  of  Glare 99 

School  Lighting,  Illumination  Values  for  Various  Rooms 98 

School  Lighting,  Laboratory 104 

Shadows 9,  20  &  71 

Shoe  Store  Lighting,  Installation  and  Plan 57 

Show  Case  Lighting 55 

Show  Window  Equipment 60 

Show  Window  Illumination  Calculations 61 

Show  Window  Lighting 59 

Show  Window  Reflectors,  Typical  Types 61 

Show  Window  and  Store  Lighting 46 

Signs,  Enclosed  Lamp 224 

Signs,    Exposed   Lamp 220 

Signs,   Flood  Lighting 230 

Sign  Lamps,   Proper   Selection   of,   Table 223 

Sign   Maintenance    231 

Sign  Lighting,  Importance  of  Adequate  Maintenance,   Diagram 232 

Sign  Lighting,  Intensities  of   Illumination,  Table 229 

Sign  Lighting,  Lamp  Spacing  to  Provide  Unbroken  Lines  of  Light,  Table  222 

Sign  Lighting,  Method  of  Avoiding  Glare 227 

Skating  Rinks   197 

State  Buildings,  Municipal  and  County 150 

Statuary    146 

Store  Lighting,  General  Classes  of 46 

Store  Lighting,  Illumination  Recommended,  Table 43 

Store  Lighting,  Lamps  Recommended,  Table 53 

Store  Lighting,  Luminiares,  Types  of 50-52 

Store  Lighting  Units  or  Luminiares 49 

Store  Lighting,  Value  or  Amount  Required 47 

Store  and  Show  Window  Lighting 46 

Street  Lighting,  Brackets  for  Small  Lamps 216 

Street  Lighting,  Business  District,  Boulevard,  Residential,  Outlying  Dis- 
tricts, Highways,  Table 208 

Street  Lighting  Fixtures,  Typical  Ornamental  Types 209 

Street  Lighting,  Modern  Practice 207 

Street  Lighting,  Necessity  of  Maintenance 217 

Street  Lighting,  Ornamental  Bracket  Standards 211 

Street  Lighting,  Pendant  Refractor  Fixtures,  Types  of 210 

Surfaces,  Surrounding,  Illumination  of 67 

Swimming  Pools    141 

Systems,  Lighting,  Maintenance  of 12 

Systematic  Maintenance   204 

Tennis   Courts,   Indoor 194 

Tennis  Courts,  Outdoor 182 

Thoroughfares    210 

Trap  Shooting  Ranges 189 

Value  of  Light  Wasted 203 

Wiring  and  Control 62 

Wiring  Diagrams  for  230  Volt  Lighting  Circuit -94 


272 


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